Mesoscale Convective Systems Observed by Cloud Sat Robert
Mesoscale Convective Systems Observed by Cloud. Sat Robert A. Houze, PI Study 1: Jasmine Cetrone Study 2: Jian Yuan Cloud. Sat Science Team Meeting, Seattle, 20 August 2008
Goal: Structure and composition of MCS Anvils ANVIL AC ANVIL AS
Study 1: Identify MCSs by tracking • West Africa • Maritime Continent • Bay of Bengal
Find MCS Anvils • Find potential MCS signal in CPR data • Track cloud systems in geostationary satellite data to decide if MCS – Tb<208 K over 100 -km scale at some point in its lifetime • Find anvil portion of CPR signal – Non-precipitating anvil if less than -10 d. BZ at all levels below 5 km
Analysis of Anvils • Number of cases: – 82 over West Africa – 78 over the Maritime Continent – 42 over the Bay of Bengal • Anvils stratified by thickness – Thin (0 -2 km), Medium (2 -6 km) and Thick (>6 km) • Plotted CFADs
All Anvil CFADs West Africa • Thin, medium, thick combined • Diagonal mode Mar. Cont. • Not as high over West Africa – Even though convection more intense – TRMM shows rain echoes higher! – Large ice particles? Bay Bengal
Thick Anvil Results West Africa • West Africa thick anvils – High reflectivity peak ~8 km another indication of larger ice Mar. Cont. • Bimodal structure at lowreflectivity values – Confirmed by ARM ground-based cloud radars – Lower maximum may be a result aggregation Bay Bengal
ARM Thick Anvil Results Niamey Darwin
Study 2: Objective Identification of MCSs • Rain Rate: AMSR-E – Aqua L 2 B Global Swath Rain Rate (AE_Rain). • Horizontal Cloud Structure: MODIS – MODIS/Aqua Clouds 1 km and 5 km 5 -Min L 2 Wide Swath Subset along Cloud. Sat V 2 at GES DISC(GES_DISC_MAC 06 S 1_v 2) • Vertical Cloud Structure: Cloud. Sat – Products 2 B-GEOPROF; 2 B-CWC-RO; 2 B-FLXHR; …
Identification of High Cloud Features MODIS Tb 11 (K) Cloud Element COMBINED AMSR/E Rain (mm/h) Rain Core FEATURE MASK
Further Analysis Identify MCSs: Rain area 2, 000 -40, 000 km 2 Mean Tb 11 <235 K Rain area with R>10 mm/hr > 200 km 2 Stratify MCSs Cold: Tb 11_min<208 K Warm: 208 Ko<Tb 11_min<220 K Subdivide Cold and Warm by size
Latitude Nº Global-seasonal distribution of MCS Largest 20 % of “Cold” MCSs (>14, 000 km 2)
Combined Analysis (CPR data in MCSs) CFAD of thick and Thin Anvils of Cold MCS
Combined Analysis Thickness-Distance Distribution for Anvils of Cold MCSs West Pacific (100 -160 E)
Conclusions & Future Work • Temporally tracked MCSs – Used manual tracking to identify MCSs – CFADs suggest larger ice particles over Africa – Thick anvils show a bimodal signature at low reflectivity confirmed by ARM cloud radars • Objective identification of MCSs – Used MODIS and AMSR E to identify MCSs – Reasonable global patterns of MCS types – Vertical structure agrees with manually tracked MCSs • Next work – Statistics of structure, composition, and radiative heating in MCS anvils
Thank You
Thank You
Study 2: Data • AMSR-E/Aqua L 2 B Global Swath Rain Rate (AE_Rain). • MODIS/Aqua Clouds 1 km and 5 km 5 -Min L 2 Wide Swath Subset along Cloud. Sat V 2 at GES DISC(GES_DISC_MAC 06 S 1_v 2) • Cloud. Sat products (2 B-GEOPROF; 2 BCWC-RO; 2 B-FLXHR…)
Latitude Nº Global-seasonal distribution of MCS Smallest 40 % of “Cold” MCSs (2000 -4900 km 2)
Vertical Structure Categories From Cloud. Sat 54 % 5% 9 % 7% 3% 45%
Methodology Build the data base of deep cloud system (precipitating and non precipitating) basd on AMSR-E rain rate and MODIS Tb 11. Group deep cloud systems into different categories based on their properties(size of the raining area, coldest Tb 11, intense raining area etc. Co-locate Cloud. Sat data with the cloud database and determine their parenting MCSs. Composite cloud structures according to their parenting MCSs.
High Cloud System identification Co-location of different datasets Picking high cloud systems 'Nearest neighbor' matching, convert AE-Rain to MODIS resolution Determining high cloud boundary based on Tb 11 gradients and rain fall pattern Determining cloud cores (raining or non-raining cold cores) in multi-core systems
MCS Definition MCS 1: Size>2000 km 2; Tb 11_min<208 Ko; Tb 11_mean<235 Ko; area with R>10 mm/hr bigger than 200 km 2 MCS 2: Size>2000 km 2, 208 Ko<Tb 11_min<228 Ko, Tb 11_mean<235 Ko; area with R>10 mm/hr bigger than 200 km 2
Global-seasonal distribution of MCS Large “Warm” MCSs (10000 -21360 km 2)
Thick Anvil Results West Africa • Bimodal structure at lowreflectivity values – Confirmed by ARM ground-based cloud radars – Lower maximum may be a result aggregation • West Africa thick anvils – Reach lower heights than other regions despite having tallest precipitation echoes – High reflectivity peak ~8 km may indicate larger ice Mar. Cont. Bay Bengal
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