Understanding the Importance of Microphysics and Macrophysics for Warm Rain in Marine Low Clouds. Part I: Satellite Observations

2009 ◽  
Vol 66 (10) ◽  
pp. 2953-2972 ◽  
Author(s):  
Terence L. Kubar ◽  
Dennis L. Hartmann ◽  
Robert Wood
Keyword(s):  
Gulf Of Mexico ◽  
Radar Data ◽  
Droplet Radius ◽  
Liquid Water Path ◽  
Cloud Radar ◽  
Warm Rain ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Cloud Tops ◽  
The Tropics

Abstract The importance of macrophysical variables [cloud thickness, liquid water path (LWP)] and microphysical variables (effective radius re, effective droplet concentration Neff) on warm drizzle intensity and frequency across the tropics and subtropics is studied. In this first part of a two-part study, Moderate Resolution Imaging Spectroradiometer (MODIS) optical and CloudSat cloud radar data are used to understand warm rain in marine clouds. Part II uses simple heuristic models. Cloud-top height and LWP substantially increase as drizzle intensity increases. Droplet radius estimated from MODIS also increases with cloud radar reflectivity (dBZ) but levels off as dBZ > 0, except where the influence of continental pollution is present, in which case a monotonic increase of re with drizzle intensity occurs. Off the Asian coast and over the Gulf of Mexico, re values are smaller (by several μm) and Neff values are larger compared to more remote marine regions. For heavy drizzle intensity, both re and Neff values off the Asian coast and over the Gulf of Mexico approach re and Neff values in more remote marine regions. Drizzle frequency, defined as profiles in which maximum dBZ > −15, increases dramatically and nearly uniformly when cloud tops grow from 1 to 2 km. Drizzle frequencies exceed 90% in all regions when LWPs exceed 250 g m−2 and Neff values are below 50 cm−3, even in regions where drizzle occurs infrequently on the whole. The fact that the relationship among drizzle frequency, LWP, and Neff is essentially the same for all regions suggests a near universality among tropical and subtropical regions.

scholarly journals Detection of multi-layer and vertically-extended clouds using A-train sensors

2009 ◽  
Vol 2 (5) ◽  
pp. 2707-2748 ◽  
Author(s):  
J. Joiner ◽  
A. P. Vasilkov ◽  
P. K. Bhartia ◽  
G. Wind ◽  
S. Platnick ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Simple Algorithm ◽  
Ozone Monitoring Instrument ◽  
Infrared Observations ◽  
Summer Hemisphere ◽  
Moderate Resolution ◽  
Cloud Optical Thickness ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
The Tropics ◽  
Cloud Top Pressure

Abstract. The detection of multiple cloud layers using satellite observations is important for retrieval algorithms as well as climate applications. In this paper, we describe a relatively simple algorithm to detect multiple cloud layers and distinguish them from vertically-extended clouds. The algorithm can be applied to coincident passive sensors that derive both cloud-top pressure from the thermal infrared observations and an estimate of solar photon pathlength from UV, visible, or near-IR measurements. Here, we use data from the A-train afternoon constellation of satellites: cloud-top pressure, cloud optical thickness, and the multi-layer flag from the Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) and the optical centroid cloud pressure from the Aura Ozone Monitoring Instrument (OMI). The cloud classification algorithms applied with different passive sensor configurations compare well with each other as well as with data from the A-train CloudSat radar. We compute monthly mean fractions of pixels containing multi-layer and vertically-extended clouds for January and July 2007 at the OMI spatial resolution (12 km×24 km at nadir) and at the 5 km×5 km MODIS resolution for infrared cloud retrievals. There are seasonal variations in the spatial distribution of the different cloud types. The fraction of pixels containing distinct multi-layer cloud is a strong function of the pixel size. Globally averaged, these fractions are approximately 20% and 5% for OMI and MODIS, respectively. These fractions may be significantly higher or lower depending upon location. There is a much smaller resolution dependence for fractions of pixels containing vertically-extended clouds (~20% for OMI and slightly less for MODIS globally), suggesting larger spatial scales for these clouds. We also find significantly higher fractions of vertically-extended clouds over land as compared with ocean, particularly in the tropics and summer hemisphere.

scholarly journals Comparison of the cloud top heights retrieved from MODIS and AHI satellite data with ground-based Ka-band radar

2019 ◽  
Author(s):  
Juan Huo ◽  
Daren Lu ◽  
Shu Duan ◽  
Yongheng Bi ◽  
Bo Liu
Keyword(s):  
Satellite Data ◽  
Radar Data ◽  
Retrieval Algorithm ◽  
Ka Band ◽  
Retrieval Accuracy ◽  
Retrieval Algorithms ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Radar Measurements ◽  
Moderate Resolution Imaging Spectroradiometer

Abstract. To better understand the accuracy of cloud top heights (CTHs) derived from passive satellite data, ground-based Ka-band radar measurements from 2016 and 2017 in Beijing were compared with CTH data inferred from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Himawari Imager (AHI). Relative to the radar CTHs, the MODIS CTHs were found to be underestimated by −1.10 ± 2.53 km and 49 % of CTH differences were within 1.0 km. Like the MODIS results, the AHI CTHs were underestimated by −1.10 ± 2.27 km and 42 % were within 1.0 km. Both the MODIS and AHI retrieval accuracy depended strongly on the cloud depth (CD). Large differences were mainly occurring for the retrieval of thin clouds of CD  1 km, the CTH difference decreased to −0.48 ± 1.70 km for MODIS and to −0.76 ± 1.63 km for AHI. MODIS CTHs greater than 6 km showed better agreement with the radar data than those less than 4 km. Statistical analysis showed that the average AHI CTHs were lower than the average MODIS CTHs by −0.64 ± 2.36 km. The monthly accuracy of both retrieval algorithms was studied and it was found that the AHI retrieval algorithm had the largest bias in winter while the MODIS retrieval algorithm had the lowest accuracy in spring.

scholarly journals A Study of the Distribution and Variability of Cloud Water Using ISCCP, SSM/I Cloud Product, and Reanalysis Datasets

2014 ◽  
Vol 27 (9) ◽  
pp. 3114-3128 ◽  
Author(s):  
Zhiwei Heng ◽  
Yunfei Fu ◽  
Guosheng Liu ◽  
Renjun Zhou ◽  
Yu Wang ◽  
...  
Keyword(s):  
Cloud Water ◽  
Positive Anomaly ◽  
Liquid Water Path ◽  
Water Path ◽  
The North ◽  
Increasing Trend ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Microwave Imager ◽  
Ice Water

Abstract In this paper, the global distribution of cloud water based on International Satellite Cloud Climatology Project (ISCCP), Moderate Resolution Imaging Spectroradiometer (MODIS), CloudSat Cloud Profiling Radar (CPR), European Center for Medium-Range Weather Forecasts Interim Re-Analysis (ERA-Interim), and Climate Forecast System Reanalysis (CFSR) datasets is presented, and the variability of cloud water from ISCCP, the Special Sensor Microwave Imager (SSM/I), ERA-Interim, and CFSR data over the time period of 1995 through 2009 is discussed. The results show noticeable differences in cloud water over land and over ocean, as well as latitudinal variations. Large values of cloud water are mainly distributed over the North Pacific and Atlantic Oceans, eastern ITCZ, regions off the west coast of the continents as well as tropical rain forest. Cloud water path (CWP), liquid water path (LWP), and ice water path (IWP) from these datasets show a relatively good agreement in distributions and zonal means. The results of trend analyzing show an increasing trend in CWP, and also a significant increasing trend of LWP can be found in the dataset of ISCCP, ERA-Interim, and CFSR over the ocean. Besides the long-term variation trend, rises of cloud water are found when temperature and water vapor exhibit a positive anomaly. EOF analyses are also applied to the anomalies of cloud water, the first dominate mode of CWP and IWP are similar, and a phase change can be found in the LWP time coefficient around 1999 in ISCCP and CFSR and around 2002 in ERA-Interim.

scholarly journals Comparison of MODIS and VIIRS cloud properties with ARM ground-based observations over Finland

2016 ◽  
Vol 9 (7) ◽  
pp. 3193-3203 ◽  
Author(s):  
Moa K. Sporre ◽  
Ewan J. O'Connor ◽  
Nina Håkansson ◽  
Anke Thoss ◽  
Erik Swietlicki ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Microwave Radiometer ◽  
Single Layer ◽  
Radar Data ◽  
Liquid Water Path ◽  
Cloud Parameters ◽  
Cloud Properties ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Biogenic Aerosols ◽  
Cloud Mask

Abstract. Cloud retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments aboard the satellites Terra and Aqua and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard the Suomi-NPP satellite are evaluated using a combination of ground-based instruments providing vertical profiles of clouds. The ground-based measurements are obtained from the Atmospheric Radiation Measurement (ARM) programme mobile facility, which was deployed in Hyytiälä, Finland, between February and September 2014 for the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) campaign. The satellite cloud parameters cloud top height (CTH) and liquid water path (LWP) are compared with ground-based CTH obtained from a cloud mask created using lidar and radar data and LWP acquired from a multi-channel microwave radiometer. Clouds from all altitudes in the atmosphere are investigated. The clouds are diagnosed as single or multiple layer using the ground-based cloud mask. For single-layer clouds, satellites overestimated CTH by 326 m (14 %) on average. When including multilayer clouds, satellites underestimated CTH by on average 169 m (5.8 %). MODIS collection 6 overestimated LWP by on average 13 g m−2 (11 %). Interestingly, LWP for MODIS collection 5.1 is slightly overestimated by Aqua (4.56 %) but is underestimated by Terra (14.3 %). This underestimation may be attributed to a known issue with a drift in the reflectance bands of the MODIS instrument on Terra. This evaluation indicates that the satellite cloud parameters selected show reasonable agreement with their ground-based counterparts over Finland, with minimal influence from the large solar zenith angle experienced by the satellites in this high-latitude location.

scholarly journals Can liquid cloud microphysical processes be used for vertically pointing cloud radar calibration?

2019 ◽  
Vol 12 (6) ◽  
pp. 3151-3171 ◽  
Author(s):  
Maximilian Maahn ◽  
Fabian Hoffmann ◽  
Matthew D. Shupe ◽  
Gijs de Boer ◽  
Sergey Y. Matrosov ◽  
...  
Keyword(s):  
Radar Data ◽  
Reference Points ◽  
Radar Reflectivity ◽  
Doppler Spectrum ◽  
Doppler Velocity ◽  
Liquid Water Path ◽  
Cloud Radar ◽  
Microphysical Processes ◽  
Radar Calibration ◽  
Sudden Decrease

Abstract. Cloud radars are unique instruments for observing cloud processes, but uncertainties in radar calibration have frequently limited data quality. Thus far, no single robust method exists for assessing the calibration of past cloud radar data sets. Here, we investigate whether observations of microphysical processes in liquid clouds such as the transition of cloud droplets to drizzle drops can be used to calibrate cloud radars. Specifically, we study the relationships between the radar reflectivity factor and three variables not affected by absolute radar calibration: the skewness of the radar Doppler spectrum (γ), the radar mean Doppler velocity (W), and the liquid water path (LWP). For each relation, we evaluate the potential for radar calibration. For γ and W, we use box model simulations to determine typical radar reflectivity values for reference points. We apply the new methods to observations at the Atmospheric Radiation Measurement (ARM) sites North Slope of Alaska (NSA) and Oliktok Point (OLI) in 2016 using two 35 GHz Ka-band ARM Zenith Radars (KAZR). For periods with a sufficient number of liquid cloud observations, we find that liquid cloud processes are robust enough for cloud radar calibration, with the LWP-based method performing best. We estimate that, in 2016, the radar reflectivity at NSA was about 1±1 dB too low but stable. For OLI, we identify serious problems with maintaining an accurate calibration including a sudden decrease of 5 to 7 dB in June 2016.

scholarly journals Identification of Small Ice Cloud Particles Using Passive Radiometric Observations

2010 ◽  
Vol 49 (11) ◽  
pp. 2334-2347 ◽  
Author(s):  
Steven J. Cooper ◽  
Timothy J. Garrett
Keyword(s):  
Near Infrared ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Regional Study ◽  
Ice Cloud ◽  
Window Technique ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
The Tropics ◽  
The Impact

Abstract There is currently significant uncertainty about the extent to which cirrus clouds are composed of “small” ice crystals smaller than about 20-μm effective radius. This is due in part to concerns that in situ measurements from aircraft are plagued by ice particle shattering on instrument inlets, artificially negatively biasing effective radii. Here, space-based measurements are applied to the problem. It is found that a space-based infrared split-window technique is less sensitive but more accurate than a visible-near-infrared technique for confident assessment of whether thin cirrus clouds have small effective radii, independent of a normal range of retrieval assumptions. Because of the sensitivities of the infrared split-window technique, however, this method can only accurately determine the presence of small particles for ice clouds with optical depths between roughly 0.5 and 3.0. Applied to Moderate Resolution Imaging Spectroradiometer (MODIS) data, it is found that a very conservative minimum of 15%–20% of such thin cirrus globally are composed of small ice crystals, but that the actual value could be as high as 40%, and even higher for cold clouds or those in the tropics. Retrievals are found to be in good agreement with airborne probe measurements from the Cirrus Regional Study of Tropical Anvils and Cirrus Layers–Florida-Area Cirrus Experiment (CRYSTAL-FACE) field campaign, implying that, for the cases examined, the impact of inlet shattering on measurements must have been limited.

scholarly journals Validation of Satellite-Based Objective Overshooting Cloud-Top Detection Methods Using CloudSat Cloud Profiling Radar Observations

2012 ◽  
Vol 51 (10) ◽  
pp. 1811-1822 ◽  
Author(s):  
Kristopher M. Bedka ◽  
Richard Dworak ◽  
Jason Brunner ◽  
Wayne Feltz
Keyword(s):  
Weather Prediction ◽  
Convective Cloud ◽  
Radar Data ◽  
Numerical Weather Prediction Model ◽  
Detection Methods ◽  
Spatial Gradients ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer

AbstractTwo satellite infrared-based overshooting convective cloud-top (OT) detection methods have recently been described in the literature: 1) the 11-μm infrared window channel texture (IRW texture) method, which uses IRW channel brightness temperature (BT) spatial gradients and thresholds, and 2) the water vapor minus IRW BT difference (WV-IRW BTD). While both methods show good performance in published case study examples, it is important to quantitatively validate these methods relative to overshooting top events across the globe. Unfortunately, no overshooting top database currently exists that could be used in such study. This study examines National Aeronautics and Space Administration CloudSat Cloud Profiling Radar data to develop an OT detection validation database that is used to evaluate the IRW-texture and WV-IRW BTD OT detection methods. CloudSat data were manually examined over a 1.5-yr period to identify cases in which the cloud top penetrates above the tropopause height defined by a numerical weather prediction model and the surrounding cirrus anvil cloud top, producing 111 confirmed overshooting top events. When applied to Moderate Resolution Imaging Spectroradiometer (MODIS)-based Geostationary Operational Environmental Satellite-R Series (GOES-R) Advanced Baseline Imager proxy data, the IRW-texture (WV-IRW BTD) method offered a 76% (96%) probability of OT detection (POD) and 16% (81%) false-alarm ratio. Case study examples show that WV-IRW BTD > 0 K identifies much of the deep convective cloud top, while the IRW-texture method focuses only on regions with a spatial scale near that of commonly observed OTs. The POD decreases by 20% when IRW-texture is applied to current geostationary imager data, highlighting the importance of imager spatial resolution for observing and detecting OT regions.

scholarly journals A study of some cloud microphysical parameters over Iraq using satellite data

2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Murtadha A. Fadhil ◽  
Kais J. Al-Jumaily
Keyword(s):  
Optical Thickness ◽  
Heavy Precipitation ◽  
Liquid Water Path ◽  
Ice Clouds ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Using Data ◽  
Earth’S Climate ◽  
Two Parameters

Studying clouds is a top priority among many atmospheric scientists because clouds are one of the greatest unknown factors in predicting changes in the Earth’s climate. Clouds play an important role in maintaining the energy balance because they can reflect, absorb, and radiate energy. The aim of this research is to investigate the properties of clouds over Iraq using data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS)on board Aqua Satellite for water and ice clouds. The results showed that daily mean cloud top pressure patterns during spring months are higher than other months and cloud top temperature patterns reached their highest values during summer months. The results also indicated that the ice cloud effective particle radius is relatively large during summer while cloud optical thickness assume its largest values in winter months. It was found that the highest values of precipitation rate over Iraq occurred during March to mid-April. Correlation aanalysis between optical thickness and liquid water path over Iraq that these two parameters are positively correlated and the correlation for water cloud was better that that for ice clouds. Case studies of heavy precipitation events over Iraq showed that the maximum values of the most cloud properties variables were located ahead of the storm center. 

scholarly journals Signature of tropical fires in the diurnal cycle of tropospheric CO as seen from Metop-A/IASI

2015 ◽  
Vol 15 (22) ◽  
pp. 13041-13057 ◽  
Author(s):  
T. Thonat ◽  
C. Crevoisier ◽  
N. A. Scott ◽  
A. Chédin ◽  
R. Armante ◽  
...  
Keyword(s):  
Quantitative Relation ◽  
Burned Area ◽  
Night Time ◽  
Fire Emissions ◽  
Diurnal Difference ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Area Product ◽  
The Tropics ◽  
The Impact

Abstract. Five years (July 2007 to June 2012) of CO tropospheric columns derived from the hyperspectral Infrared Atmospheric Sounding Interferometer (IASI) on-board Metop-A are used to study the impact of fires on the concentrations of CO in the troposphere. Following Chédin et al. (2005, 2008), who found a quantitative relation between the daily tropospheric excess of CO2 and fire emissions, we show that tropospheric CO also displays a diurnal signal with a seasonality that agrees well with the seasonal evolution of fires given by Global Fire Emission Database version 3 (GFED3.1) and Global Fire Assimilation System version 1 (GFAS1.0) emissions and Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 5 burned area product. Unlike day- or night-time CO fields, which mix local emissions with nearby emissions transported to the region of study, the day–night difference of CO allows to highlight the CO signal due to local fire emissions. A linear relationship between CO fire emissions from the GFED3.1 and GFAS1.0 inventories and the diurnal difference of IASI CO was found over various regions in the tropics, with a better agreement with GFAS1.0 (correlation coefficient of R2 ∼ 0.7) than GFED3.1 (R2 ∼ 0.6). Based on the specificity of the two main phases of the combustion (flaming vs. smoldering) and on the vertical sensitivity of the sounder to CO, the following mechanism is proposed to explain such a CO diurnal signal: at night, after the passing of IASI at 21:30 local time (LT), a large amount of CO emissions from the smoldering phase is trapped in the boundary layer before being uplifted the next morning by natural and pyroconvection up to the free troposphere, where it is seen by IASI at 09:30 LT. The results presented here highlight the need to take into account the specificity of both the flaming and smoldering phases of fire emissions in order to fully take advantage of CO observations.

scholarly journals Impact of the Vertical Variation of Cloud Droplet Size on the Estimation of Cloud Liquid Water Path and Rain Detection

2007 ◽  
Vol 64 (11) ◽  
pp. 3843-3853 ◽  
Author(s):  
Ruiyue Chen ◽  
Fu-Lung Chang ◽  
Zhanqing Li ◽  
Ralph Ferraro ◽  
Fuzhong Weng
Keyword(s):  
Liquid Water ◽  
Cloud Droplet ◽  
Cloud Base ◽  
Liquid Water Path ◽  
Vertical Variation ◽  
Water Path ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Cloud Liquid Water Path ◽  
Mean Square Errors

Abstract Cloud droplet effective radius (DER) and liquid water path (LWP) are two key parameters for the quantitative assessment of cloud effects on the exchange of energy and water. Chang and Li presented an algorithm using multichannel measurements made at 3.7, 2.1, and 1.6 μm to retrieve a cloud DER vertical profile for improved cloud LWP estimation. This study applies the multichannel algorithm to the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data on the Aqua satellite, which also carries the Advanced Microwave Scanning Radiometer (AMSR-E) for measuring cloud LWP and precipitation. By analyzing one day of coincident MODIS and AMSR-E observations over the tropical oceans between 40°S and 40°N for overcast warm clouds (>273 K) having optical depths between 3.6 and 23, the effects of DER vertical variation on the MODIS-derived LWP are reported. It is shown that the LWP tends to be overestimated if the DER increases with height within the cloud and underestimated if the DER decreases with height within the cloud. Despite the uncertainties in both MODIS and AMSR-E retrievals, the result shows that accounting for the DER vertical variation reduces the mean biases and root-mean-square errors between the MODIS- and AMSR-E–derived LWPs. Besides, the manner in which the DER changes with height has the potential for differentiating precipitative and nonprecipitative warm clouds. For precipitating clouds, the DER at the cloud top is substantially smaller than the DER at the cloud base. For nonprecipitating clouds, however, the DER differences between the cloud top and the cloud base are much less.

Sign in / Sign up

Export Citation Format

Share Document