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Mesoscale Convective Systems in Amazonia in the Wet Season Maria Assunção F. Silva Dias Departamento de Ciências Atmosféricas Instituto Astronômico e.

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Presentation on theme: "Mesoscale Convective Systems in Amazonia in the Wet Season Maria Assunção F. Silva Dias Departamento de Ciências Atmosféricas Instituto Astronômico e."— Presentation transcript:

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2 Mesoscale Convective Systems in Amazonia in the Wet Season Maria Assunção F. Silva Dias Departamento de Ciências Atmosféricas Instituto Astronômico e Geofísico Universidade de São Paulo

3 Why are clouds important in LBA?

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7 Shallow cumulus layer Mixed layer Tracer continuity equation in the mixed layer

8 Water vapor morning

9 Freitas et al, 2000 GOES-8 visible satellite image at 11:45 UTC March 16, 1998, showing the smoke produced by biomass burning over Roraima state. GOES-8 IR satellite image at 18:00 UTC March 18, 1998 showing the convective system at northern part of Amazon basin.

10 Freitas et al, 2000

11 cloud model Convective trajectory equations mesoscale, regional model Freitas et al, 2000

12 Non-convective trajectories Convective trajectories CO 2 CO

13 1. Observations 2. Internal controls on convection 3. External controls on convection

14 1. Observations

15 TRMM-LIS Seasonal (DJF, JJA, SON) 12/97 - 1/00 Petersen et al, 2000

16 TRMM-PR 2A-25 RELATIVE FREQ. HISTOGRAMS Continental ??Ocean Petersen et al, 2000

17 Height (km) TRMM-PR IWC (Z-M) vs. LIS Flash Density LAND OCEAN AMZ (SON) AMZ (DJF)

18 Wet Season Mesoscale Atmospheric Campaign LBA January and February, 1999 Rondônia WETAMC Components: FAPESPs: Mesoscale Interactions between Biosphere and Atmosphere in LBA FAPESPs: Atmospheric Chemistry/LBA EUSTACH NASA - TRMM/LBA

19 Objectives to understand the coupling between biosphere and atmosphere processes in the wet season in the Amazon region including budgets of heat, water vapor, trace gases and VOC; to determine the cloud dynamics and microphysics interactions over rain forest and over adjacent deforested areas including the role of aerosol and biogenic compounds as CCN; to understand the local response of clouds and rainfall to large scale forcing; to improve modeling of biosphere-atmosphere processes in different scales.

20 Observations four radiosonde sites performing 6-8 soundings per day, three tethered balloon sites for boundary layer meteorology; 1 forest 60 m micrometeorological tower instrumented with 3 levels of eddy correlation measurements and vertical profiles of radiation, temperature, humidity and windspeed; 1 forest 54 m tower instrumented for atmospheric chemistry measurements, including CO2 flux. forest and pasture arrays for temperature and soil moisture and set of rings for soil respiration. 1 tethered ballon for atmospheric chemistry measurements, 2 pasture towers with profiles, and eddy correlation measurements including CO2 flux.

21 1 pasture tower for atmospheric chemistry measurements and spectral radiation measurements 2 wind profiler sodars, 1 with RASS network of 4 complete AWS; 4-station lightning detection network, a dense raingauge network and several disdrometers, 2 Doppler radars (including the NCAR S-pol and the TOGA C-band radar), a dual-wavelength radar profiler Citation II Learjet for in-situ sampling of microphysical variables ER-2 carrying the EDOP radar (ER-2 Doppler, X band radar) and AMPR (Airborne Microwave Profiling Radiometer), a multi-frequency radiometer similar to the SMI instrument on TRMM.

22 Rondônia

23 WETAMC sites

24 Fisher et al 2000 LBA winter LBA summer Kwajalein

25 Downscaling with RAMS 20 km grid

26 Rondônia Low Levels Wind Regimes 13 Jan - 18 Jan... Westerly 19 Jan - 26 Jan... Easterly 27 Jan - 2 Feb... Westerly 2 Feb - 21 Feb... Easterly 22 Feb - 28 Feb...Westerly Rickembach et al, 2000

27 Easterly Westerly Carvalho et al 2000

28 Rickenbach et al. 2000

29 Blakeslee, 2000 w WW

30 Westerly case Easterly case S-pol Rondônia Petersen et al, 2000

31 Carvalho et al, 2000

32 Average accumulated rainfall from net 1 Ji-Paraná airport area W W W

33 Tokai, 2000

34 2. Internal controls.

35 Convective dynamics (Cotton & Anthes, 1989)

36 Cotton & Anthes, 1989 Wallace & Hobbs, 1972 (a) condensation (b) collection Warm rain processes

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38 Wallace & Hobbs, 1972 Seinfeld & Pandis,1998

39 Cloud condensation nuclei in Amazonia in the wet season - primary organic aerosol - secondary organic aerosol: add soluble material (sulfates) to particles that come from elsewhere or ar nucleated at clod tops. G.Roberts, 2000 M. Andrea, 2000

40 TRMM observed first direct evidence of smoke from forest fires inhibiting rainfall Rosenfeld D GEOPHYSICAL RESEARCH LETTERS 26: (20) OCT Although it has been known that smoke from biomass burning suppresses warm rain processes, it was not known to what extent this occurs. The satellite observations of the Tropical-Rainfall- Measuring-Mission (TRMM), presented here, show that warm rain processes in convective tropical clouds infected by heavy smoke from forest fires are practically shut off. The tops of the smoke-infected clouds must exceed the freezing level, i.e., grow to altitudes colder than about -10 degrees C, for the clouds to start precipitating. In contrast, adjacent tropical clouds in the cleaner air precipitate most of their water before ever freezing. There are indications that rain suppression due to air pollution prevails also in the extra-tropics.

41 Cold rain processes Cotton & Anthes, 1989

42 Williams et al, 1999 (Westerly) (Easterly) (End of dry season) (Easterly) (Westerly)

43 3. External controls

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45 Cutrim et al, 1995, BAMS

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47 7 Feb 1999

48 7 February 1999 R NET rain LE H ABRACOS- BR/EC 7 Feb 1999

49 Development of the CBL Fisch et al, 2000

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52 Easterly Westerly Carvalho et al 2000

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54 CPTEC/INPE ANALYSIS

55 24Feb99

56 Pereira et al, 2000

57 12Z 26 Jan e 0Z 27Jan

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60 Cohen et al, 1989 Amazonian Squall Lines

61 Silva Dias e Ferreira, 1992 EWNSN Average soundings in Belém at 12 UTC during GTE/ABLE 2B II - Coastal Convective lines IV - 5 consecutive days with squall lines I - All squall line days III - No convective lines

62 Cohen et al, 1995 May 4 May 5 May 6 Wind 700 hPa (Atlantic Easterly Wave)

63 Vórtice Ciclônico de Altitude

64 Average accumulated rainfall from net 1 Ji-Paraná airport area W W W

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66 Summary - shallow cumulus respond to in different ways in the wet and dry seasons. Does that impact rainfall? - large scale forcing (dynamics, thermodynamics) imposes a mode of convection which has a symbiotic relationship with cloud microphysics and CCN.

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