Abstract: We report on studies of the lidar and the depolarization ratios for cirrus clouds. The optical depth and effective lidar ratio are derived from the transmission of clouds, which is determined by comparing the backscattering signals at the cloud base and cloud top. The lidar signals were fitted to a background atmospheric density profile outside the cloud region to warrant the linear response of the return signals with the scattering media. An average lidar ratio, 29 +/- 12 sr, has been found for all clouds measured in 1999 and 2000. The height and temperature dependences ofthe lidar ratio, the optical depth, and the depolarization ratio were investigated and compared with results of LITE and PROBE. Cirrus clouds detected near the tropopause are usually optically thin and mostly subvisual. Clouds with the largest optical depths were found near 12 km with a temperature of approximately -55 degrees C. The multiple-scattering effect is considered for clouds with high optical depths, and this effect lowers the lidar ratios compared with a single-scattering condition. Lidar ratios are in the 20-40 range for clouds at heights of 12.5-15 km and are smaller than approximately 30 in height above 15 km. Clouds are usually optically thin for temperatures below approximately -65 degrees C, and in this region the optical depth tends to decrease with height. The depolarization ratio is found to increase with a height at 11-15 km and smaller than 0.3 above 16 km. The variation in the depolarization ratio with the lidar ratio was also reported. The lidar and depolarization ratios were discussed in terms of the types of hexagonal ice crystals.

Abstract: Due to its unique nine-angle configuration, the Multi-angle Imaging SpectroRadiometer (MISR) can retrieve cloud parameters such as cloud-motion vectors and cloud-top heights using a purely geometrical technique that involves locating the same cloud features at different viewing angles. The geometrical nature of this technique means that the retrievals are relatively insensitive to the absolute instrument calibration. Fast stereo-matching algorithms have been developed to perform this image matching automatically on an operational basis. Preliminary results are shown of the operational retrievals together with comparisons against other data. Cloud-top height is generally obtained on a 1.1-km grid with an accuracy of /spl plusmn/ 562 m, even over snow and ice. The limitations of the technique, resulting at times in height blunders, noisy retrievals, and discrete effects of wind correction, are discussed.

Abstract: This study investigates the recovery of the tropical atmosphere to moist conditions following the arrival of a dry intrusion observed during the Tropical Ocean and Global Atmosphere Program Coupled Ocean–Atmosphere Response Experiment (TOGA COARE). A cloud-resolving model was used to quantify the processes leading to the moistening of the lower and middle troposphere. The model replicates the general recovery of the tropical atmosphere. The moisture field in the lower and middle troposphere recovered in large part from clouds repeatedly penetrating into the dry air mass. The moistening of the dry air mass in the simulation was due to lateral mixing on the edges of cloudy regions rather than mixing at cloud top. While the large-scale advection of moisture played a role in controlling the general evolution of moisture field, the large-scale thermal advection and radiation tend to directly control the evolution of the temperature field. The diurnal variations in these two terms were largely responsi...

Abstract: A parameterization of shallow cumulus clouds for use in atmospheric general circulation models is proposed. The parameterization uses a bulk representation of an ensemble of transient clouds. Entrainment of environmental air occurs at the ascending top of the cumulus cloud and also at the lateral boundaries of the region below the top of the cloud. Complete detrainment of the air in the cloud occurs when the top of the cloud reaches its maximum height, chosen to be the level of neutral buoyancy. The parameterization is calibrated using results from the undisturbed period of the Barbados Oceanographic and Meteorological Experiment (BOMEX). Vertical profiles of in-cloud properties and mass fluxes obtained from large eddy simulations (LES) for the undisturbed BOMEX period are successfully reproduced by the parameterization. Good agreement is also found in comparisons with large-scale heat and moisture budgets diagnosed from observations during the same period of the experiment. However, this is achieved with a different choice for the parameters of the scheme.

Abstract: Some observations suggest that the volcanic aerosols produced by the Mt. Pinatubo eruption may have altered cirrus properties. We look for evidence that such modification of cirrus is extensive enough to be climatically significant by comparing three satellite-based cirrus datasets produced by the ISCCP (International Satellite Cloud Climatology Project) analysis, the 'split-window' analysis, and 3I analysis. Since the former two have not been compared in detail before, we conduct such a comparison here. When applied to AVHRR (Advanced Very High Resolution Radiometer) data, both the ISCCP and split-window analyses identify about 0.2 - 0.3 cirrus cloud amount in tropical latitudes; however, there are detailed differences of classification for about half of these clouds. The discrepancies are attributed to the simplified assumptions made by both methods. The latter two datasets are derived from infrared radiances, so they are much less sensitive to volcanic aerosols than the ISCCP analysis. After the Mt. Pinatubo eruption, the ISCCP results indicate a dramatic decrease of thin cirrus (cloud top pressure less than 440 mb and visible optical thickness less than 1.3) over ocean, accompanied by a comparable increase of altocumulus and cumulus clouds; over land, there are no significant changes. In contrast, results from the split-window and 3I analyses show little change in thin cirrus amount over either ocean or land that is associated with the volcanic eruption. The ISCCP results can, therefore, be understood as a misclassification of thin cirrus because the additional reflected sunlight by the volcanic aerosol makes the cirrus clouds appear to be optically thicker. Examination of the split-window signature and the infrared emissivities from 3I show no significant change in infrared emissivity (or optical thickness). These results indicate that the Mt. Pinatubo volcanic aerosol did not have a significant systematic effect on tropical cirrus properties, but rather produced only temporary, local effects. Hence, these results indicate that there was no significant climate feedback produced by aerosol-cirrus-radiative interactions.

Abstract: This paper introduces a methodology to retrieve cloud base heights from electro-optical (EO) imagery and demonstrates the approach with MODerate resolution Imaging Spectroradiometer (MODIS) data collected by NASA's EOS Terra mission. In earlier investigations, the value of cloud top heights and total integrated water vapour was demonstrated as constraints in the retrieval of moisture profiles from microwave moisture sounder data. From the analyses of temporally and spatially coincident Defense Meteorological Satellite Program (DMSP) F-11 and NOAA-10 satellite sensor data, the existence of a cloud base signature appeared evident using external knowledge of cloud top temperatures. More recently, simulations were conducted to determine the sensitivity of observed brightness temperatures to variations in cloud base height and other cloud properties. These studies confirmed the presence of a cloud base spectral signature in microwave moisture sounder data for water clouds, when cloud top temperatures are known...

Abstract: A challenging problem in snow mapping is the discrimination of snow from clouds. Snow and clouds often have similar spectral reflectance features across the spectrum and may have similar temperatures making discrimination difficult. Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the NASA Earth Observing System (EOS) Terra spacecraft, is used to generate many geophysical products including snow extent and cloud properties. MODIS snow and cloud mask data products have been generated in a consistent series from 1 November 2000 to the present. The MODIS snow algorithm uses the cloud mask data product to identify clouds. The MODIS cloud mask algorithm employs many cloud spectral tests to determine if a pixel is cloud or clear; a cloud mask summary flag as well as all the cloud spectral tests applied are stored in the product. The production version of the MODIS snow algorithm uses the cloud mask summary flag to discriminate snow from cloud. The cloud conservative nature of the cloud mask algorithm generally results in more cloud obscuration than necessary, relevant to snow identification, which has impacted the ability to map snow extent. Analysis of the cloud mask algorithm techniques, processing paths and cloud tests, has led to improved usage of cloud spectral test data for masking clouds in the snow algorithm. Described are refinements in the use of cloud tests from the cloud mask product that minimize cloud obscuration of snow cover, maximize snow identification and constrain confusion between snow and clouds, leading to an improved mapping of snow cover extent.

Abstract: [1] The EOS-TERRA MODIS and MISR instruments provide radiances for independent spectral and stereo retrievals of cloud top height (CTH), respectively. Collocated and coincident CTH retrievals were compared against each other and with coincident millimeter-wavelength cloud radar (MMCR) retrievals over the British Isles and the ARM SGP site. This inter-comparison suggests close agreement between MMCR, MODIS and MISR when they detect the same CTHs. When MISR detected high clouds, MISR stereo CTH was generally higher than MODIS CO2-slicing CTH. However, for large areas in most of the 27 scenes studied here, high clouds were detected by MODIS but not by MISR. These high clouds occurred during periods of multi-layered clouds. Inspection of all off-nadir MISR radiances during these periods indicated that MISR has sufficient sensitivity to detect these clouds, but not with the innermost 3 MISR cameras used for stereo CTH retrieval.

Abstract: This article describes a stereo-photogrammetric method for simultaneous retrieval of cloud advection and cloud-top height fields using multi-angle imagery from the MISR instrument. Although stereoscopy has been widely used for topographic surface retrieval, its application to dynamic cloud elevations has been very limited. This article shows theoretically that, by using multiple MISR camera look angles from satellite altitudes, cloud advection and cloud-top height can be separated stereoscopically, thus enabling their simultaneous retrieval. A completely automatic retrieval algorithm was designed and implemented, including steps for multi-angle image registration on a reference Earth ellipsoid surface, mesoscale cloud advection derivation employing stereoscopic retrieval, and simultaneous stereoscopic reduction of high-resolution cloud-top heights. Before instrument launch, numerical simulations were implemented to demonstrate the feasibility of the retrieval, and to derive estimates of the algorithm errors. Since launch, stereo cloud reduction from MISR has been routinely processed for global climatological studies.

Abstract: A 1D infrared radiative transfer model that handles clouds with subgrid-scale horizontal variability is developed and tested. It assumes that fluctuations in cloud absorptance optical depth k across layers (and collections of layers) can be described by gamma distributions. Unlike homogeneous clouds, flux incident at a level inside a horizontally inhomogeneous cloud requires explicit computation of transmittance to all other levels in the cloud. Consequently, in addition to estimates of variability for each layer, variability between any two levels must be specified too. Scattering by hydrometeors and a general treatment of cloud overlap are included in this model. Solutions for isothermal and nonisothermal Planck source functions are presented. For the synthetic cloudy atmospheres used here, the new model produces errors for outgoing longwave radiation (OLR) and cloud cooling rates that are typically more than an order of magnitude smaller than those associated with the conventional homogeneous cloud model (as used in all GCMs at present). It is shown that up- and downwelling fluxes and cloud cooling rates can depend much on subgrid-scale variability. For high overcast clouds with realistic variability, OLR can be up to 20 W m 22 more than that predicted by a conventional homogeneous model using the same mean k. At the same time, cooling rate errors at cloud top and cloud base due to the homogeneous assumption can be up to 625%; the sign depending primarily on mean k and magnitude of variability. For lower, thicker clouds, the homogeneous assumption leads primarily to errors in cloud-top cooling. The new code usually remedies these errors greatly. This model, and its solar counterpart, are used currently in the Canadian Centre for Climate Modelling and Analysis GCM.

Abstract: An idealized model of the relationship between entrainment in cloud-topped boundary layers, circulation structure, and the degree of decoupling between the cloud and subcloud layers is developed based on simple turbulent flux distributions and the premise that the entrainment rate, both at cloud top and across cloud base when some stability exists there, is controlled by the large-eddy structure for quasi-steady buoyantly driven conditions. Layers are classified in three regimes depending on whether the cloud-top entrainment rate is ultimately limited by the transport of eddies spanning the full boundary layer (I), the cloud layer (II), or the subcloud layer (III). Algebraic relations are derived for the boundaries between, and entrainment fluxes in, each regime as a function of a convenient set of physical input parameters. The transition from regime II into III, representing the decoupling transition leading to a cumulus coupled layer, is emphasized. The model predicts that decoupling is promoted by a decrease in Bowen ratio or increase in cloud-top humidity to temperature jump ratio, and, depending on the point in parameter space, either promoted or inhibited by an increase in cloud-top radiative cooling or an increase in cloud depth. In spite of the complex cloud-layer dynamics involving cumulus plumes, a simple prediction is given for the quasi-steady cloud-top entrainment rate in regime III based on the subcloud dynamics. The model is compared with results from an extensive set of large-eddy simulations varying surface heat and moisture fluxes, cloud-top humidity and temperature jumps, and relative cloud depth. Good agreement is found with the predicted entrainment rates, the qualitative layer structure, and location of the decoupling boundary in the parameter space varied.

Abstract: The Polarization and Directionality of the Earth's Reflectance (POLDER) spatial polarimeter was onboard the Advanced Earth Observation Satellite (ADEOS) satellite that flew from August 1996 to June 30, 1997. POLDER measured both multidirectional reflectance and polarization in visible and near-infrared spectral bands with a very wide field of view. An accurate absolute radiometric calibration is essential for the scientific exploitation of radiance measurements of the Earth. POLDER inflight radiometric calibration has been performed at the Centre National d'Etudes Spatiales (CNES), French National Space Studies Center, from measurements taken only on well-characterized targets. This paper presents the results of the POLDER in-flight radiometric interband calibration over clouds for channels 443 and 490 nm. The method is based on the comparison of measurements to simulations. Selected measurements correspond to observations over oceans for high, thick convective cumulonimbus and for low, thick stratocumulus. Simulations are calculated using the discrete ordinate computing method. An error budget considers the sensitivity of this calibration method to cloud microphysics, to cloud top altitude, and to aerosols and gaseous loading. Calibration results are discussed for different simulated cloud models.

Abstract: [1] In this paper, an inversion algorithm for the retrieval of total density, pressure, and temperature in the Earth's lower atmosphere from refraction angle measurements by a visible-light imager is presented. A detailed description of the retrieval algorithm is provided, and its performance under a variety of conditions is assessed, including a rigorous evaluation of the statistical and systematic uncertainties. Tests show that visible-light images of stellar refraction can provide reasonably accurate measurements of the atmospheric bulk properties from the surface (or cloud top heights) to roughly 30 km altitude. The combined statistical and systematic uncertainties in density and temperature profiles retrieved with a vertical resolution of 1 km decrease from 3.1% and 5 K, respectively, at 30 km to 0.8% and 3.8 K at 20 km and 0.35% and 1.5 K at 10 km for an imager with a sampling rate of 10 Hz and pointing control/knowledge of 0.002° (1σ). This level of accuracy and resolution is adequate for a combined extinctive/refractive occultation technique for remotely sensing the Earth's lower atmosphere that has recently been demonstrated using data taken by the Ultraviolet and Visible Imagers and Spectrographic Imagers (UVISI) on the Midcourse Space Experiment (MSX) spacecraft.

Abstract: Energy-balancemodels driven by radiation and turbulent heat fluxes have been widely applied to predicting the response of the Greenland ice sheet to climate change. However, a lack of knowledge of the temporal and spatial distribution of cloud amount and type has necessitated the use of parameterizations or statistical models of cloud cover. This deficiency results in large uncertainties in both shortwave and longwave radiation fluxes. Stereo-matching of nadir and forward view AlongTrack Scanning Radiometer-2 (ATSR-2) image pairs has been shown to be a reliable method of retrieving cloud top height, and further cloud properties can be derived from thermal imagery allowing classification into cloud type. A 1 year cloud record for a transect across southern Greenland derived from stereo-matching is presented here, and comparisons are made with climate re-analysis data and ground observations. The cloud-cover data were used in a simple radiative transfer model, and the impact of clouds on the net radiation fluxes was found to be considerable. Different cloud scenarios produced up to 40 Wm–2 difference in net radiation balance. In the ablation zone, where the albedo is lower and most variable, the sensitivity to cloud-cover fraction was less marked, but the higher spatial resolution of the ATSR-2 cloud record was reflected by a much more varied trend in radiation balance. Whether the net radiation balance increases or decreases with increased cloud cover was found to be a function of the cloud amount and type and also the surface albedo. The sensitivity of the model to a ±5% change in cloud amount was found to be comparable to a 1 K change in temperature. This clearly demonstrates the importance of reliable, quantitative cloud data in mass-balance and other glaciological studies.

Abstract: Mesoscale cloud properties complement the point measurements of similar parameters at the Atmospheric Radiation Measurement (ARM) surface sites. To improve upon the climatology of satellite-derived cloud properties over the ARM Southern Great Plains (SGP) domain, a pair of multi-spectral algorithms, the Visible-Infrared-Solar Infrared-Split Window Technique (VISST) and Solar Infrared-Station (SIRS) method, respectively, was developed and is currently being applied on a near-real-time basis. Because the nighttime algorithms are still being improved, only the daytime data are considered fully operational. The VISST cloud mask has been improved to discriminate between clouds and snow, and utilizes an improved parameterization of visible (0.65 µm) reflectance. This paper describes the results from the analysis of data taken since January 2000 on a half-hourly basis.

Abstract: Lightning is an important source for nitrogen oxides (NO x ) in the atmosphere. To differentiate between the impact of lightning produced NO x and anthropogenic NO x emissions on the global atmospheric chemistry, we present a simulation of flash densities and the corresponding NO x emissions from the global climate chemistry model ECHAM4.L39(DLR)/CHEM (E39/C). The basis for a realistic simulation of flash densities is the realistic representation of deep convection in the model E39/C. This will be validated by observations from the International Satellite Cloud Climatology Project (ISCCP). We will discuss the difficulties that arise, when cloud parameters from these satellite measurements will be compared with the corresponding properties taken from a global model. The flash densities in E39/C are represented by a new lightning parameterization that connects the flash frequency of a thunderstorm with the convective air mass transport within the thunderstorm cell. This property is a reasonable and physically based indicator for lightning within a deep convective cloud. The number of convective events is simulated realistically by E39/C. The simulated heights of convective cloud tops are consistent with the observations. However, in midlatitudes over Europe, the simulated cloud top heights seem to be underestimated. The flash densities show a good agreement with the OTD observations, although the ratio of flash densities over land and over the oceans seems to be underestimated. In midlatitudes over Europe, the simulated flash densities are too low compared to the observations, this can be explained through the shortcomings of the convection parameterization. The simulated NO x emissions show maxima in the tropics and in the midlatitudes, being separated significantly from the aircraft emissions. The maximum values of lightning NO x emissions (in terms of ng(N) s -1 m -3 ), lying approximately 5 km below the tropopause, are higher than the corresponding emissions from aircrafts by a factor of three. Furthermore, the maximum aircraft emissions tend to be at higher altitude and farther north compared to the lightning NO x production.

Abstract: [1] We have innovated a remote sensing methodology involving the retrieval of three-dimensional ice water content and ice crystal mean size of cirrus clouds based on a unification of satellite and ground-based cloud profiling radar observations. This methodology has been applied to AVHRR/NOAA satellite data and mm-wave cloud radar data obtained from the DOE's ARM program in northern Oklahoma. The three-dimensional cloud parameter fields thus constructed are assessed with ice crystal size distributions independently derived from measurements by optical probes on board the University of North Dakota Citation. The retrieved three-dimensional ice water contents and mean effective ice crystal sizes involving an impressive cirrus cloud occurring on April 18, 1997, are shown to be comparable to those derived from the analysis of collocated and coincident in situ aircraft measurements.

Abstract: The bi-spectral threshold (BTH) for cloud detection and height assignment is now operational at NASA's Global Hydrology and Climate Center (GHCC) This new approach is similar in principle to the bi-spectral spatial coherence (BSC) method with improvements made to produce a more robust cloud-filtering algorithm for nighttime cloud detection and subsequent 24-hour operational cloud top pressure assignment The method capitalizes on cloud and surface emissivity differences from the GOES 39 and 107-micrometer channels to distinguish cloudy from clear pixels Separate threshold values are determined for day and nighttime detection, and applied to a 20-day minimum composite difference image to better filter background effects and enhance differences in cloud properties A cloud top pressure is assigned to each cloudy pixel by referencing the 107-micrometer channel temperature to a thermodynamic profile from a locally -run regional forecast model This paper and supplemental poster will present an objective validation of nighttime cloud detection by the BTH approach in comparison with previous methods The cloud top pressure will be evaluated by comparing to the NESDIS operational CO2 slicing approach

Abstract: In order to bring large amounts of precipitation, the new seeding method using liquid carbon dioxide (LC) was suggested by Fukuta (1996a). The method was applied to the supercooled convective cloud in a post-frontal weather condition in northern Kyushu, Japan, on October 27 1999. In the seeding experiment, LC seeding and the subsequent observation by aircraft were carried out and the features of a seeded echo were observed by radar. Consequently, the aircraft observation confirmed the further development of the seeded cumulus together with a fuzzy aspect of the cloud surface, which indicates the feature consisting of ice particles. Furthermore, the observed cloud top was quite consistent with the cloud top estimated by the thermodynamic analysis following parcel theory. Therefore, the observed results indicate the artificial effects by LC seeding. On the other hand, the radar observation confirmed an artificially induced echo, which showed spreading of the echo area and took a unique mushroom shape in the RHI pictures. The maximum width of the echo reached 24 km and the total amount of estimated radar precipitation of the seeded cumulus was approximately 2.4 million ton, traversing a distance of 60 km in 1 h 40 min. The observed and estimated results are consistent with the hypothesis of the new seeding method, which induces the dynamic and microphysical processes consisting of two fundamental processes. In addition, it was found that dynamical interaction between the seeded and the adjacent natural cumuli was an important factor in the formation of the secondary cumulus. The observational fact will give new viewpoint into the future seeding study. Copyright © 2002 John Wiley & Sons, Ltd.

Abstract: Significant enhancements in humidity around cumulus clouds, that is, the “cloud halos” observed in many aircraft penetrations, are simulated using a three-dimensional dynamic model. Five case studies show that humidity halos occur mainly near lateral cloud boundaries and also occur at cloud top and base when the cloud dissipates. The humidity halo broadens as the cloud ages and is also broader in the presence of wind shear than in its absence, especially on the downshear side of the cloud. The broadband calculation over the solar spectrum (0.2–4.0 μm) shows that the shortwave (SW) heating rate in the halo is about 11%–18% larger than the ambient environmental heating rate. The strongest halo-induced surface SW radiative forcing for all cases studied is about −0.2 W m^−2, which is approximately a 0.02% change from the forcing without a halo.

Abstract: We have studied the cloud and precipitation features in the Indian summer monsoon region based on satellite microwave and infrared observations. Emphases are particularly given to the differences between stratiform and convective rains and between rains over land and over ocean. In the studied region, average rainfall rate of convective clouds is about 6 times higher than for stratiform clouds while the latter covers 4 to 5 times more area than the former. As a result, convective rains produce higher rain total than stratiform rains with a ratio of about 3 : 2. The difference between convective and stratiform rains is evident virtually by any satellite signatures – cloud top temperature, and microwave emission, scattering and combined signatures. Cloud top temperature appears no skill to reflect surface rainfall rates for stratiform rains while colder cloud top temperatures correspond to higher rainfall rates for convective clouds. As rainfall rate increases, microwave emission signature reaches saturation much quicker for stratiform rains than for convective rains. For convective rains, the rainfall rate – scattering signature relation shows a distinct difference between rains over land and over ocean. Corresponding to the same rainfall rate, the scattering signature over land is about twice as high as that over ocean. The mean vertical precipitation profiles showed that stratiform rains have a constant rainfall rate below freezing level and a sharp drop-off above, regardless over land or ocean. Convective rain profiles, on the other hand, often have the maximum rainfall rate below the freezing level, implying a significant growth of raindrops by warm microphysical processes, such as coalescence. It is also found that given the same surface rainfall rate, the amount of ice particles above freezing level is substantially greater for convective rains over land than over ocean, which explains the difference of scattering signatures between rains over the two different surface types. It is also demonstrated that the sub-pixel variability of rains is largely responsible for the mismatch between plane-parallel model simulations and actual satellite observations.

Abstract: The Vaisala ceilometer LD-40 'Tropopauser' is a compact eye-safe lidar measuring continuously under all possible climatic conditions and scanning the atmosphere up to a height of 13000 m. It uses laser diodes with 855 nm wavelength that are pulsed at an average frequency of 4000 Hz. The distance of the system's range bins is 7.5 m. Its main purpose is reporting cloud base heights and vertical visibility for aviation safety purposes. This paper focuses on the additional parameters this affordable lidar is able to report due to its advanced technical properties. These parameters include kind of precipitation detected, presence and distance of cirrus, extinction coefficients within clouds, vertical profiles of planetary boundary layer backscatter power, and a comparison of cloud coverage detected by a ceilometer with values obtained with a total cloud coverage scanner. Comparison instruments include regular radiosonde soundings performed at the Meteorological Observatory Lindenberg of the German Weather Service.

Abstract: [1] The retrieval of cirrus cloud microphysical properties in a multilayer cloud system is a challenge due to the usually low optical thickness of the ice cloud under investigation. However, it is estimated that about 50% of all cirrus clouds occur in such multilayer systems. Here, we present a method that uses a combination of five observations by the dual-view ATSR-2 radiometer onboard the ERS-2 satellite. Using the channels at 0.87 and 1.6 μm in both nadir and forward views and the nadir view of the 3.7 μm band, the retrieval can clearly separate a thin high cloud from a highly reflective low water cloud and thus determine the optical thickness and effective particle size of the cirrus quantitatively. This is confirmed by a comparison of the retrieved parameters with in situ aircraft observations made on 23 March 2000 near Punta Arenas, Chile, where good agreement was observed. An important finding of this study was that the pixel-to-pixel variability of the low cloud cannot be neglected. In other words, the optical thickness of the low cloud needs to be included as a retrieval parameter, because the assumption of constant optical properties leads to large degree of uncertainties in the derived ice cloud parameters.

Abstract: This study investigates and accounts for the influence of various ice cloud parameters on the retrieval of the surface solar radiation budget (SSRB) from reflected flux at the top of the atmosphere (TOA). The optical properties of ice clouds depend on ice crystal shape, size distribution, water content, and the vertical profiles of geometric and microphysical structure. As a result, the relationship between the SSRB and TOA-reflected flux for an ice cloud atmosphere is more complex and differs from that for water cloud and cloudless atmospheres. The sensitivities of the relationship between the SSRB and TOA-reflected flux are examined with respect to various ice cloud parameters. Uncertainties in the retrieval of the SSRB due to inadequate knowledge of various ice cloud parameters are evaluated thoroughly. The uncertainty study is concerned with both pure ice clouds and multiphase clouds (ice cloud above water cloud). According to the magnitudes of errors in the SSRB retrieval caused by different input variables, parameterized correction terms were introduced. If the input variables are known accurately, errors in the retrieval of the SSRB under a wide range of ice cloud conditions are expected to diminish substantially, to less than 10 W m−2 for 91% of the simulated ice cloud cases. In comparison, the same accuracy may be attained for only 19% of the retrievals for the same ice cloud cases using the retrieval algorithm designed for non-ice-cloud conditions.

Abstract: Based on the research results that already have, the new cloud and snow identificating factors were presented through analysing the spectrum characteristics of cloud and snow in the NOAA AVHRR image, moreover, the experiment proved that the identificating method between snow and cloud is good enough in southern Qinghai, it gained expected effect.

Abstract: There are ten channels in Chinese FY-1C polar orbiting meteorological satellite. These channels cover visible, near infrared and infrared spectral bands. Based on our simulating analysis of thermodynamic phase of cloud top particles, a case study using FY-1C data is performed. Results show that FY-1C channel 6 (1.58–1.64 µm) can be used to analyze the thermodynamic phase of cloud particles.