Aerosol Effects on the General Circulation and Atmospheric Water Cycle

1
Aerosol Effects on the General Circulation and
Atmospheric Water Cycle

• William K. M. Lau
• Laboratory for Atmospheres
• NASA/GSFC
• Contributors M. K. Kim, K. M. Kim, Y. C. Sud,
  M. Chin, G. Walker, C. Hsu, S. C. Tsay, B.
  Holben, W. Tao, A. DaSilva

2
Water vapor, clouds precipitation and dynamical
feedback

Direct effect
Blocks sunlight, cools surface - dimming effect
Semi-direct effect
Atmospheric Water Cycle
Increased stability less convection
Aerosols
alters heating gradients, convection and
circulation
Indirect effect 1st kind
Brightens clouds
Indirect effect 2nd kind
Suppresses or Increases rainfall
Aerosol chemistry, transport, deposition and A-A
interaction
3
Major Activities on aerosol-atmospheric water
cycle dynamicsin Earth-Sun Division

• Science Highlights
• Atmospheric teleconnection induced by absorbing
  aerosols during boreal spring (Kim et al. 2006,
  J. Climate)
• Asian monsoon anomalies induced by direct aerosol
  effects the role of the Tibetan Plateau (Lau et
  al. 2006 ,Climate Dynamics)
• Effects of heating by atmospheric dust on West
  African monsoon and Sahel rainfall (Lau et al)
• Parameterization of indirect effect, including
  CCN activation, nucleation processes with cloud
  microphysics (Sud, Wilcox et al)
• CRM and MMF modeling of aerosol 2nd direct
  effects, and cloud radiation feedback (Tao et al)
• Programs/Field Campaigns
• WCRP/CEOP major initiative on aerosol-monsoon
  interaction, and intermonsoon studies.
• Rajo-Megha (dust cloud) international field
  campaigns in Indo-Gangetic Plain,
  Himalayas/Tibet, western China.
• NASA AMMA field campaign

4
Why aerosols and monsoon?

• Over 60 of world population live in monsoon
  countries
• Monsoon related droughts and floods, and aerosols
  are the two most severe environmental hazards in
  monsoon regions, e.g. Asia and West Africa
• The monsoon water cycle is driven by atmospheric
  heating, through the dynamical interaction of
  wind, moisture, clouds and rainfall.
• Sea surface temperature, and land surface
  processes alter monsoon water cycle, through
  generation of surface heating gradients and
  atmospheric heat sources and sinks.
• Suspended particles (aerosol, clouds,
  precipitation) in the atmosphere regulate and
  interact with heat sources and sinks in ways we
  dont understand

5
Aerosol induced surface air temperature anomalies
from NASA fvGCM (AA-NA) experiments
Lau et al 2006, Climate Dynamics
6
Model anomalous heating due to shortwave
absorption by aerosols (dust and black carbon)
over the slopes of the Tibetan Plateau
7
The Elevated Heat Pump (EHP) hypothesis (Lau et
al 2006)
In July-August, the increased convection spreads
from the foothills of the HImalayas to central
India, resulting in an intensification of the
Indian monsoon.
8
GLAS/ICESat
9
TOMS Aerosol Index
MAM
10
(No Transcript)
11
Holben et al
12
(No Transcript)
13
Recent Trends (1979-2004) in absorbing aerosol
and India Monsoon Rainfall
Increasing trend of monsoon rainfall, and TOMS AI
over IG basin (GPCP) in MJ
MJ wet-north dry-south JA wet
all-India Validation of EHP hypothesis (???)
14
Africa Monsoon Multiscale Analysis (AMMA) Project
North Africa is the worlds major source of
mineral dust aerosol
Dust outbreak along the coast of West Africa, 16
June 1999. A SeaWiFS image shows a large dust
outbreak passing over Dakar (on the peninsula
projecting from the coast) and extending in a
broad arc over the Cape Verde Islands. Dust is
also seen blowing from sources along the coast of
Mauritania north of Dakar. The inset is a TOMS
Absorbing Aerosol Product image on the same day.
The TOMS product has an advantage over SeaWiFS in
that it shows the distribution of dust over land
thereby serving as a useful tool for identifying
dust sources and transport paths.
15
fvGCM simulations AA-NA
16
Dust-induced intensification and northward
migration of the WAM rainbelt
17
E-W cross-section
N-S cross-section
18
Elevated Heat Pumpeffect of aerosol-water cycle
dynamics over the Atlantic/Caribbean region
increased upper level clouds
reduced upper level clouds
induced subsidence suppresses convection
dust source
increased low level clouds
reduced SW cools land
increased moisture influx
increases local pollution
Africa
reduced SW
reduced latent heat flux
warms ocean
cools ocean
Caribbean Region
19
RAJO-MEGHA( dust cloud in Sanskrit) An
Initiative (Phase0) to NASA Roadmap on Global
Fresh Water Redistribution
(Radiation, Aerosol Joint Observations - Monsoon
Experiment in Gangetic-Himalayan Area)
Si-Chee Tsay and W.Lau, and the GSFC Team NASA
Goddard Space Flight Center
P. K. Bhartia, B. N. Holben, N. C. Hsu, Q. Ji,
Y. Sud, M. D. King, L. A. Remer, J. S. Schafer,
E. J. Welton, V. Ramanathan (UCSD),T. Koike
(Japan), G. Tartari (Italy), P. Ginoux (NOAA),
R. Singh (India), G. Wu (China)
20
Objective

• To determine the role of absorbing aerosols,
  especially with regarding to elevated heat
  sources and interaction with black carbon, in
  affecting the water-cycle dynamics of the Indian
  summer monsoon
• Integrated (aerosol, cloud, and precipitation and
  large scale circulation) measurements approach
• Aerosol and cloud characteristics
• Sources/sinks, and transport processes
• Elevated vs. boundary layer AERONET,
  ground-based, radar/lidar, local aircraft, and
  satellite remote sensing
• Phase-I (April-May, aerosol forcing), Phase-II
  (May-June, water cycle response)
• Monitoring in surrounding regions, by
  collaborating with other international programs,
  i.e., ABC, Indian Ocean Monitoring (CLIVAR),
  GEWEX, and CEOP.

21
(No Transcript)
22
Near Future Afternoon ConstellationA-Train
130 PM
138 PM
115 PM
Cloudsat
OMI - Cloud heights OMI HIRLDS Aerosols MLS
TES - H2O temp profiles MLS HIRDLS Cirrus
clouds
MODIS/CERES - IR Properties of Clouds AIRS -
Temperature and H2O Sounding
CALIPSO
Aqua
OCO - CO2 column
PARASOL
OCO
Aura
CALPSO- Aerosol and cloud heights Cloudsat -
cloud droplets PARASOL - aerosol and cloud
polarization