scholarly journals Cloud invigoration and suppression by aerosols over the tropical region based on satellite observations

2011 ◽  
Vol 11 (2) ◽  
pp. 5003-5017 ◽  
Author(s):  
F. Niu ◽  
Z. Li
Keyword(s):  
Satellite Observations ◽  
Mixed Phase ◽  
Tropical Region ◽  
Cloud Properties ◽  
Tropical Oceans ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Microphysical Processes ◽  
Mixed Phase Clouds

Abstract. Aerosols may modify cloud properties and precipitation via a variety of mechanisms with varying and contradicting consequences. Using a large ensemble of satellite data acquired by the Moderate Resolution Imaging Spectroradiometer onboard the Earth Observing System's Aqua platform, the CloudSat cloud profiling radar and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite over the tropical oceans, we identified two distinct responses of clouds and precipitation to increases in aerosol loading. Cloud-top temperatures decrease significantly with increasing aerosol index (AI) over oceans and aerosol optical depth (AOT) over land for mixed-phase clouds with warm cloud bases; no significant changes were found for liquid clouds. The distinct responses are explained by two mechanisms, namely, the aerosol invigoration effect and the microphysical effect. Aerosols can significantly invigorate convection mainly through ice processes, while precipitation from liquid clouds is suppressed through aerosol microphysical processes. Precipitation rates are found to increase with AI for mixed-phase clouds, but decrease for liquid clouds, suggesting that the dominant effect differs for the two types of clouds. These effects change the overall distribution of precipitation rates, leading to more or heavier rains in dirty environments than in cleaner ones.

scholarly journals Reconciling Simulated and Observed Views of Clouds: MODIS, ISCCP, and the Limits of Instrument Simulators

2012 ◽  
Vol 25 (13) ◽  
pp. 4699-4720 ◽  
Author(s):  
Robert Pincus ◽  
Steven Platnick ◽  
Steven A. Ackerman ◽  
Richard S. Hemler ◽  
Robert J. Patrick Hofmann
Keyword(s):  
Optical Thickness ◽  
Model Error ◽  
Diagnostic Tools ◽  
Limited Information ◽  
Global Models ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Cloud Top Pressure

Abstract The properties of clouds that may be observed by satellite instruments, such as optical thickness and cloud-top pressure, are only loosely related to the way clouds are represented in models of the atmosphere. One way to bridge this gap is through “instrument simulators,” diagnostic tools that map the model representation to synthetic observations so that differences can be interpreted as model error. But simulators may themselves be restricted by limited information or by internal assumptions. This paper considers the extent to which instrument simulators are able to capture essential differences between the Moderate Resolution Imaging Spectroradiometer (MODIS) and the International Satellite Cloud Climatology Project (ISCCP), two similar but independent estimates of cloud properties. The authors review the measurements and algorithms underlying these two cloud climatologies, introduce a MODIS simulator, and detail datasets developed for comparison with global models using ISCCP and MODIS simulators. In nature MODIS observes less midlevel cloudiness than ISCCP, consistent with the different methods used to determine cloud-top pressure; aspects of this difference are reproduced by the simulators. Differences in observed distributions of optical thickness, however, are not captured. The largest differences can be traced to different approaches to partly cloudy pixels, which MODIS excludes and ISCCP treats as homogeneous. These cover roughly 15% of the planet and account for most of the optically thinnest clouds. Instrument simulators cannot reproduce these differences because there is no way to synthesize partly cloudy pixels. Nonetheless, MODIS and ISCCP observations are consistent for all but the optically thinnest clouds, and models can be robustly evaluated using instrument simulators by integrating over the robust subset of observations.

scholarly journals Estimates of the vertical distribution of desert dust and conden-sation nuclei over the Mediterranean, with the synergistic use of active and passive remote sensing techniques

2017 ◽  
Author(s):  
Ελένη Μαρίνου
Keyword(s):  
Atmospheric Model ◽  
Satellite Observations ◽  
Desert Dust ◽  
Passive Remote Sensing ◽  
Regional Atmospheric Model ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Remote Sensing Techniques ◽  
The Vertical Distribution

Ο πρωταρχικός στόχος αυτής της εργασίας είναι να καλύψει υπάρχοντα κενά στην αντίληψή μας σχετικά με το ρόλο της ερημικής σκόνης στις κλιματικές παραμέτρους της Μεσογείου χρησιμοποιώντας προηγμένες μεθόδους τηλεπισκόπησης. Αρχικά, η ερημική σκόνη διαχωρίζεται από τα συνολικά αερολύματα που παρέχονται από σύγχρονους δορυφορικούς αισθητήρες τηλεπισκόπησης. Το προϊόν σκόνης που παράγεται χρησιμοποιείται στην ανάπτυξη της τρισδιάστατης κατανομής του φόρτου της σκόνης πάνω από τη Μεσόγειο και τη Βόρεια Αφρική, η οποία είναι πολύ σημαντική για την επίδραση της σκόνης στην ηλιακή ακτινοβολία. Τέλος, αναπτύσσουμε κλιματολογίες των συγκεντρώσεων της σκόνης που ενεργούν ως πυρήνες παγoποίησης, για τη μελέτη της επίδρασης της σκόνης στο σχηματισμό νεφών.Η μεθοδολογία μας περιλαμβάνει τη συνέργεια παθητικών και ενεργών μετρήσεων τηλεπισκόπησης, με έμφαση στις κατακόρυφες μετρήσεις των αερολυμάτων που παρέχονται από το δορυφορικό lidar του CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations). Αρχικά, αναπτύσσουμε ένα νέο προϊόν σκόνης χρησιμοποιώντας τις μετρήσεις του CALIPSO, βασιζόμενοι σε μεθοδολογίες που έχουν αναπτυχθεί στο πλαίσιο του Ευρωπαικού επίγειου δικτύου lidar EARLINET (AErosol RObotic NETwork). Ο διαχωρισμός της σκό-νης από τους άλλους τύπους αερολυμάτων γίνεται χρησιμοποιώντας τα προφίλ του συντελεστή οπισθοσκέδασης και του λόγου αποπόλωσης του CALIPSO, καθώς και τις μετρήσεις και τις μεθόδους του EARLINET. Το προϊόν αξιολογείται με μετρήσεις από το δίκτυο AERONET (AEr-osol RObotic NETwork) και συγκρίνεται με δορυφορικές παρατηρήσεις από το MODIS (Moderate Resolution Imaging Spectroradiometer) και με κατακόρυφα προφίλ από το μοντέλο BSC-DREAM8b (Barcelona Supercomputer Center - Dust Regional Atmospheric Model). Το νέο προϊόν σκόνης χρησιμοποιείται για την παραγωγή μιας τρισδιάστατης κλιματολογίας της εξέλιξης της Σαχαριανής σκόνης πάνω από την Βόρεια Αφρική και την Ευρώπη, χρησιμοποιώντας τις δορυφορικές παρατηρήσεις του CALIPSO από το 2007 έως το 2015. Τα αποτελέσματα αναδεικνύουν την τρισδιάστατη εξέλιξη της σκόνης και τις εποχιακές διαδρομές της μεταφοράς της από τη Σαχάρα προς τη Μεσόγειο και την ηπειρωτική Ευρώπη. Το νέο προϊόν σκόνης είναι ελεύθερα διαθέσημο (κατόπιν αιτήσεως αλλά και από διάφορες ιστοσελίδες) και έχει ήδη χρησιμοποιηθεί από την παγκόσμια μετεωρολογική οργάνωση, την ευρωπαϊκή υπηρεσία διαστήματος και από συνεργάτες ερευνητές για την αξιολόγηση 3 μοντέλων μεταφοράς σκόνης, νέων προϊόντων από δορυφόρους πολικής και γεωστατικής τροχιάς και για την μελέτη της επίδρασης της σκόνης στο ισοζύγιο της ακτινοβολίας. Εδώ παρουσιάζονται τρία παραδείγματα τέτοιων εφαρμογών, με πρώτο (α) τη βελτιστοποίηση των παραμέτρων ενός μοντέλου μεταφοράς σκόνης προκειμένου να περιγραφεί η καταιγίδα σκόνης στη Μέση Ανατο-λή και την Ανατολική Μεσόγειο συνέβει το 2015, β) την κατηγοριοποίηση αερολυμάτων από το διάστημα με σκοπό τον διαχωρισμό των αερολυμάτων ανθρωπογενούς και φυσικής προέλευσης και (γ) την αξιολόγηση διαφορετικών παραμετροποιήσεων σκόνης σε περιφερειακά κλιματικά μοντέλα. Τέλος, ανακτώνται οι κατακόρυφες κατανομές συγκέντρωσης πυρήνων παγοποίησης στην περιοχή της μελέτης. Αυτό το αποτέλεσμα παρέχει μια μοναδική ευκαιρία για μελλοντική έρευνα πάνω στον ετερογενή σχηματισμού του πάγου, χρησιμοποιώντας παρατηρήσεις νεφών.

scholarly journals Aerosols and Clouds Interactions in an Urban Atmosphere

2020 ◽  
Vol 237 ◽  
pp. 02004
Author(s):  
Indira Gunaseelan ◽  
Vijay Bhaskar
Keyword(s):  
Urban Air Pollution ◽  
Urban Atmosphere ◽  
Annual Variations ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Extensive Collection ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Aerosol Emissions ◽  
Precipitation Reduction

Aerosols create great uncertainties in studying climate change under global warming and atmospheric dynamics. To understand the impacts of aerosols on cloud properties in Madurai, we have analyzed an extensive collection of aerosol and cloud properties, obtained from the Moderate resolution Imaging Spectroradiometer (MODIS) data, over the study site during 2012-2013. Monthly, seasonal and annual variations of aerosols and clouds studied along their interactions and impacts on climate. Considering annual averages for all these parameters, most often the year 2012 was dominated with a higher presence of AOD, COD, CER, CTT, CTP whereas rainfall and CF were found to be dominated in 2013. The presence of higher CF in 2013 may be a cause for the higher rainfall and the lower level of CF in 2012 may be a cause for less rainfall. High aerosol loading in this area is due to biomass burning and urban air pollution which may significantly suppress precipitation. Increased aerosols and the local aerosol emissions may reduce the precipitation efficiency, which is responsible for the precipitation reduction and vice-versa.

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

2014 ◽  
Vol 14 (19) ◽  
pp. 26003-26039 ◽  
Author(s):  
T. Thonat ◽  
C. Crevoisier ◽  
N. A. Scott ◽  
A. Chédin ◽  
R. Armante ◽  
...  
Keyword(s):  
Burned Area ◽  
Tropical Region ◽  
Fire Emissions ◽  
Diurnal Difference ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Emissions Inventories ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
The Impact ◽  
Local Emissions

Abstract. Five years (July 2007–June 2012) of CO tropospheric columns derived from the IASI hyperspectral infrared sounder onboard Metop-A are used to study the impact of fires on the concentrations of CO in the mid-troposphere. Following Chédin et al. (2005, 2008), who showed the existence of a daily tropospheric excess of CO2 quantitatively related to fire emissions, we show that tropospheric CO also displays a diurnal signal with a seasonality that is in very good agreement with the seasonal evolution of fires given by GFED3.1 (Global Fire Emission Database) emissions and MODIS (Moderate Resolution Imaging Spectroradiometer) burned area. Unlike daytime or nighttime 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 is found in the whole tropical region between CO fire emissions from the GFED3.1 inventory and the diurnal difference of IASI CO (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 9.30 p.m. 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 pyro-convection up to the free troposphere, where it is seen by IASI at 9.30 a.m. LT. The results presented here highlight the need for developing complementary approaches to bottom-up emissions inventories and for taking 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 Forecasting Carbon Monoxide on a Global Scale for the ATom-1 Aircraft Mission: Insights from Airborne and Satellite Observations and Modeling

2018 ◽  
Author(s):  
Sarah A. Strode ◽  
Junhua Liu ◽  
Leslie Lait ◽  
Róisín Commane ◽  
Bruce Daube ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Optical Thickness ◽  
Global Scale ◽  
Satellite Observations ◽  
Aerosol Optical Thickness ◽  
Large Contribution ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Typical Summer

Abstract. GEOS-5 forecasts and analyses show considerable skill in predicting and simulating the CO distribution and the timing of CO enhancements observed during the ATom-1 aircraft mission. Using tagged tracers for CO, we find a dominant contribution from non-biomass burning sources along the ATom transects except over the tropical Atlantic, where African biomass burning makes a large contribution to the CO concentration. One of the goals of ATom is to provide a chemical climatology over the oceans, so it is important to consider whether August 2016 was representative of typical summer conditions. Using satellite observations of 700 hPa and column CO from the Measurement of Pollution in the Troposphere (MOPITT) instrument, 215 hPa CO from the Microwave Limb Sounder (MLS), and aerosol optical thickness from the Moderate Resolution Imaging Spectroradiometer (MODIS), we find that CO concentrations and aerosol optical thickness in August 2016 were within the observed range of the satellite observations, but below the decadal median for many of the regions sampled. This suggests that the ATom-1 measurements may represent relatively clean but not exceptional conditions for lower tropospheric CO.

scholarly journals Clouds and the Earth’s Radiant Energy System (CERES) FluxByCldTyp Edition 4 Data Product

2022 ◽  
Keyword(s):  
Radiative Transfer ◽  
Radiant Energy ◽  
Energy System ◽  
Cloud Type ◽  
Radiative Transfer Models ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Transfer Models

Abstract The Clouds and the Earth’s Radiant Energy System (CERES) project has provided the climate community 20 years of globally observed top of the atmosphere (TOA) fluxes critical for climate and cloud feedback studies. The CERES Flux By Cloud Type (FBCT) product contains radiative fluxes by cloud-type, which can provide more stringent constraints when validating models and also reveal more insight into the interactions between clouds and climate. The FBCT product provides 1° regional daily and monthly shortwave (SW) and longwave (LW) cloud-type fluxes and cloud properties sorted by 7 pressure layers and 6 optical depth bins. Historically, cloud-type fluxes have been computed using radiative transfer models based on observed cloud properties. Instead of relying on radiative transfer models, the FBCT product utilizes Moderate Resolution Imaging Spectroradiometer (MODIS) radiances partitioned by cloud-type within a CERES footprint to estimate the cloud-type broadband fluxes. The MODIS multi-channel derived broadband fluxes were compared with the CERES observed footprint fluxes and were found to be within 1% and 2.5% for LW and SW, respectively, as well as being mostly free of cloud property dependencies. These biases are mitigated by constraining the cloud-type fluxes within each footprint with the CERES Single Scanner Footprint (SSF) observed flux. The FBCT all-sky and clear-sky monthly averaged fluxes were found to be consistent with the CERES SSF1deg product. Several examples of FBCT data are presented to highlight its utility for scientific applications.

scholarly journals Examination of POLDER/PARASOL and MODIS/Aqua Cloud Fractions and Properties Representativeness

2011 ◽  
Vol 24 (16) ◽  
pp. 4435-4450 ◽  
Author(s):  
Shan Zeng ◽  
Frédéric Parol ◽  
Jérôme Riedi ◽  
Céline Cornet ◽  
François Thieuleux
Keyword(s):  
Cloud Cover ◽  
Temporal Variations ◽  
Cloud Fraction ◽  
Atmospheric Sciences ◽  
Cloud Parameters ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Level 2

Abstract The Polarization and Anisotropy of Reflectances for Atmospheric Sciences Coupled with Observations from a Lidar (PARASOL) and Aqua are two satellites on sun-synchronous orbits in the A-Train constellation. Aboard these two platforms, the Polarization and Directionality of Earth Reflectances (POLDER) and Moderate Resolution Imaging Spectroradiometer (MODIS) provide quasi simultaneous and coincident observations of cloud properties. The similar orbits but different detecting characteristics of these two sensors call for a comparison between the derived datasets to identify and quantify potential uncertainties in retrieved cloud properties. To focus on the differences due to different sensor spatial resolution and coverage, while minimizing sampling and weighting issues, the authors have recomputed monthly statistics directly from the respective official level-2 products. The authors have developed a joint dataset that contains both POLDER and MODIS level-2 cloud products collocated on a common sinusoidal grid. The authors have then computed and analyzed monthly statistics of cloud fractions corresponding either to the total cloud cover or to the “retrieved” cloud fraction for which cloud optical properties are derived. These simple yet crucial cloud statistics need to be clearly understood to allow further comparison work of the other cloud parameters. From this study, it is demonstrated that on average POLDER and MODIS datasets capture correctly the main characteristics of global cloud cover and provide similar spatial distributions and temporal variations. However, each sensor has its own advantages and weaknesses in discriminating between clear and cloudy skies in particular situations. Also it is shown that significant differences exist between the MODIS total cloud fraction (day mean) and the “retrieved” cloud fraction (combined mean). This study found a global negative difference of about 10% between POLDER and MODIS day-mean cloud fraction. On the contrary, a global positive difference of about 10% exists between POLDER and MODIS combined-mean cloud fraction. These statistical biases show both global and regional distributions that can be driven by sensors characteristics, environmental factors, and also carry potential information on cloud cover structure. These results provide information on the quality of cloud cover derived from POLDER and MODIS and should be taken into account for the use of other cloud products.

scholarly journals Evaluation of Cloud Mask and Cloud Top Height from Fengyun-4A with MODIS Cloud Retrievals over the Tibetan Plateau

2021 ◽  
Vol 13 (8) ◽  
pp. 1418
Author(s):  
Wenjing Xu ◽  
Daren Lyu
Keyword(s):  
Tibetan Plateau ◽  
Climate Science ◽  
The Tibetan Plateau ◽  
Cloud Detection ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
New Generation ◽  
Cloud Mask

The Tibetan Plateau (TP) has profound thermal and dynamic influences on the atmospheric circulation, energy, and water cycles of the climate system, which make the clouds over the TP the forefront of atmospheric and climate science. However, the highest altitude and most complex terrain of the TP make the retrieval of cloud properties challenging. In order to understand the performance and limitations of cloud retrievals over the TP derived from the state-of-the-art Advanced Geosynchronous Radiation Imager (AGRI) onboard the new generation of Chinese Geostationary (GEO) meteorological satellites Fengyun-4 (FY-4), a three-month comparison was conducted between FY-4A/AGRI and the Moderate Resolution Imaging Spectroradiometer (MODIS) for both cloud detection and cloud top height (CTH) pixel-level retrievals. For cloud detection, the AGRI and MODIS cloud mask retrievals showed a fractional agreement of 0.93 for cloudy conditions and 0.73 for clear scenes. AGRI tended to miss lower CTH clouds due to the lack of thermal contrast between the clouds and the surface of the TP. For cloud top height retrievals, the comparison showed that on average, AGRI underestimated the CTH relative to MODIS by 1.366 ± 2.235 km, and their differences presented a trend of increasing with height.

scholarly journals Impacts of Partly Cloudy Pixels on Shortwave Broadband Irradiance Computations

2019 ◽  
Vol 36 (3) ◽  
pp. 369-386 ◽  
Author(s):  
Seung-Hee Ham ◽  
Seiji Kato ◽  
Fred G. Rose
Keyword(s):  
Solar Zenith Angle ◽  
Cloud Fraction ◽  
Similar Magnitude ◽  
Cloud Optical Depth ◽  
Cloud Properties ◽  
Moderate Resolution ◽  
Satellite Sensors ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
First Time

AbstractBecause of the limitation of the spatial resolution of satellite sensors, satellite pixels identified as cloudy are often partly cloudy. For the first time, this study demonstrates the bias in shortwave (SW) broadband irradiances for partly cloudy pixels when the cloud optical depths are retrieved with an overcast and homogeneous assumption, and subsequently, the retrieved values are used for the irradiance computations. The sign of the SW irradiance bias is mainly a function of viewing geometry of the cloud retrieval. The bias in top-of-atmosphere (TOA) upward SW irradiances is positive for small viewing zenith angles (VZAs) <~60° and negative for large VZAs >~60°. For a given solar zenith angle and viewing geometry, the magnitude of the bias increases with the cloud optical depth and reaches a maximum at the cloud fraction between 0.2 and 0.8. The sign of the SW surface net irradiance bias is opposite of the sign of TOA upward irradiance bias, with a similar magnitude. As a result, the bias in absorbed SW irradiances by the atmosphere is smaller than the biases in both TOA and surface irradiances. The monthly mean biases in SW irradiances due to partly cloudy pixels are <1.5 W m−2 when cloud properties are derived from Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Aqua.

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