AEROSOLINDIRECT

Study of Aerosol Indirect Effects in China

15 May 2008 - 29 December 2008

Lead Scientist: Zhanqing Li

Observatory: AMF , HFE

Aerosols in China have exceptionally high loading and diverse properties, and their influence has been detected across the Pacific Rim. The rapid pace of changes in the atmospheric environment over China provides a natural testbed for identifying and quantifying the climatic effects of aerosols. Preliminary analyses of multiple satellite data sets (MODIS, TMI, TRMM) indicated more complex and unique aerosol indirect effects than what is found in relatively cleaner environments. Unfortunately, China is one of the least observed regions, especially in terms of aerosol and cloud properties. To verify the satellite findings and gain a deeper understanding requires either in situ measurements or independent ground-based remote sensing data, or ideally both. To this end, the ARM Mobile Facility (AMF) was deployed in China in 2008 to enhance observation capability of a funded project to achieve the following goals:

• Acquisition of essential cloud, aerosol, and meteorological parameters using the AMF to validate satellite-based findings
• Use of AMF measurements together with validated satellite retrievals and in situ data to understand the mechanisms of the aerosol indirect effects in the region
• Examination of the roles of aerosols in affecting regional climate and atmospheric circulation with a special focus on the impact of the East Asian monsoon system.

Researchers tested the following scientific hypotheses through the AMF deployment in China:

• Aerosols play a major role in the inconsistent results from rain remote sensing.
• Aerosol loading in China is so heavy that it significantly affects the dynamics of the monsoon system.
• Aerosol types and meteorological conditions in China are so diverse that they have distinct climatic effects.

Testing these hypotheses required AMF, satellite and aircraft observations of the following variables:

• Aerosol optical (optical depth, single scattering albedo, etc.), microphysical (size distribution), and chemical (composition) properties, as well as vertical profiles
• Cloud properties (cloud fraction, cloud optical depth, cloud liquid water path, location of cloud layers, cloud phase, etc.)
• Radiative quantities (total broadband and narrowband spectral radiances and irradiances, direct and diffuse irradiances)
• Thermodynamic and dynamical properties (e.g., atmospheric soundings and cloud updraft velocities).

Researchers chose to study the Yangtze delta region in southeast China, the center of the satellite rainfall retrieval anomaly and also the area where the aerosol optical depth distribution in China is maximal. Continuous measurements were made for some of the key variables listed above for nearly a year prior, thanks to the logistical and scientific support provided by personnel at the Chinese Academy of Sciences.