Tropical Cloud Population

Transcription

1 Tropical Cloud Population

2 Before Satellites

3 Visual Observation View from and aircraft flying over the South China Sea

4 Radiosonde Data Hot tower hypothesis Riehl & Malkus 1958

5 Satellite Observations

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8 Post satellite view of tropical cloud population, ca 1970 The cirrus shield was introduced Explained satellite pictures and retained the hot tower notion and the fact that smaller clouds exist. But missing are downdrafts, mesoscale stratiform rain and thick anvils. Also assumes simple scale separation.

9 Radars

10 GATE 1974

11 GATE SHIP ARRAY

12 More Tropical Field Projects TEPPS 1997 EPIC 2001 BoB 1979 JASMINE 1999 (Dashed: No sounding network)

13 Figure CONVSF MCS precipitation subdivided into convective and stratiform components Houze 1997 Old convection Vigorous convection 100 km Houze 1997

14 Convective Vigorous convection Note Max w > (V T ) snow Height Distance Houze 1997

15 Stratiform Old convective material Note (V T ) snow ~1-2 m/s Height Distance Houze 1997

16 Idealized life cycle of tropical MCS Houze 1982

17 Post-GATE view of the tropical cloud population Houze et al. (1980)

18 Precipitation Radar in Space

19 The TRMM Satellite Radar TRM M Low altitude, low inclination orbit

20 TRMM Satellite Instrumentation! = 2 mm Important! PR measures 3D structure of radar echoes Kummerow et al, 1998

21 Global precipitation seen from space Combined satellite rainfall July 2000 TRMM plus passive microwave sensors + other

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23 Latent Heating Max rain in tropics varies zonally Combined satellite rainfall July 2000

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25 2 Years of TRMM PR data Large Cbs MCSs Small isolated Cbs Schumacher & Houze 2003

26 Trade Wind Regime

27 Indo/Pacific Warm Pool

28 Traditional conceptual view of mean meridional distribution of tropical convection

29 Trimodal distribution Johnson et al Based on TOGA COARE data

30 Johnson et al TOGA COARE

31 Convective Structure as a Function of Large-scale Context SST Ocean vs Land Land Surface Type Coastal Effects Mountains Synoptic Situation

32 SST

33 TRMM PR Deep Convective SST Climatology (July) July SST TRMM PR Shallow, Isolated Convective

34 Land vs Ocean

35 West African Squall Line

36 Global frequency and distribution of lightning as observed from space Christian et al.2002.

37 TRMM view of Africa vis a vis the Atlantic Rain Stratiform Rain Fraction MCSs with large 85 GHz ice scattering Lightning

38 South Asian Monsoon Land Surface Mountains Synoptic Context

39 Terrain gradients Land-ocean contrast Land cover differences Thar Desert Ganges Delta Snow/Ice Tundra Wetland Forest Irrigated crop Crop Savanna Shrub/Grass Dryland/crop Grass Shrub Barren

40 Mean Large-scale Flow Pattern at 1000 mb and 200 mb

41 Analysis Subregions N Western Subregion Mountain Foothills Lowland Central Subregion Eastern Subregion Arabian Sea INDIA Bay of Bengal E

42 Analysis of three-dimensional echo regions Used TRMM algorithm for separating echoes into stratiform & convective regions! STRATIFORM identified by 2 criteria: Existence of bright band Lack of intense echo cores! Non-stratiform is either CONVECTIVE or OTHER OTHER

43 To study the vertical structure of convective regions we first define 3D echo cores The TRMM Precipitation Radar data are provided in bins ~5 km in the horizontal and ~0.25 km in the vertical Echo cores are formed by contiguous bins (in 3D space) of reflectivity values which exceed the threshold of 40 dbz. echo core 3D radar echo bounded by 40 dbz contour land

44 Examples Deep Convective Core Wide Convective Core Stratiform Convective Broad Stratiform Region

45 Western Central Eastern Deep Intense Cores 40 dbz echo > 10 km in height Wide Intense Cores 40 dbz echo > 1000 km 2 area Broad Stratiform Echo stratiform echo > 50,000 km 2

46 Carlson et al dry,hot moist

47 Sawyer 1947

48 Backward trajectories (HYSPLIT/NCEP) 2.5 km 1.0 km Medina et al. 2010

49 WRF Simulation Mixing ratio CAPE Medina et al. 2010

50 WRF Simulation Isochrones of integrated hydrometeor content Hydrometeor mixing ratio just after convection formed Medina et al. 2010

51 Intraseasonal Variation of the Monsoon 39 events Break Day 0: 8 mm/d 5N-5S 80-90E Active Webster & Tomas 1997

52 Broad stratiform case 11 Aug UTC

53 Broad stratiform case Upstream of mountains 0455 UTC

54 Reflectivity data for 2 monsoon seasons " Convection is stronger & deeper in west " Stratiform more pronounced in east

55 Propagating MCSs

56 Cross section of MCS with leading line of convection and trailing stratiform precipitation Houze et al. 1989

57 Squall Line With Trailing Stratiform Precipitation TRMM PR data over West Africa This one propagates E to W assisted by midlevel African easterly jet

58 A squall-line in India rare rare! Himalayas 2017 UTC 5 June 2003

59 A squall-line in India rare rare! Himalayas 500 mb jet over and parallel to the Himalayas 10 meter level 500 mb level 5 June 2003

60 Cloud Radar in Space

61 Combining 3 Types of Satellite

62 MCSs Over the Whole Tropics Yuan and Houze 2010

63 MCSs Over the Whole Tropics Yuan and Houze 2010

64 MCSs Over the Whole Tropics Yuan and Houze 2010 Frequency of MCS anvil cloud

65 MCSs Over the Whole Tropics Yuan and Houze 2010 MCS Anvil cloud properties derived from CloudSat Thickness (km) West Africa Indian Ocean Normalized Distance