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Wesley Berg, Tristan L’Ecuyer, and Sue van den Heever Department of Atmospheric Science

Evaluating the impact of aerosols on the onset and microphysical properties of rainfall off the coast of China. Wesley Berg, Tristan L’Ecuyer, and Sue van den Heever Department of Atmospheric Science Colorado State University. Differences in TRMM Rainfall Detection February 1, 2000.

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Wesley Berg, Tristan L’Ecuyer, and Sue van den Heever Department of Atmospheric Science

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  1. Evaluating the impact of aerosols on the onset and microphysical properties of rainfall off the coast of China Wesley Berg, Tristan L’Ecuyer, and Sue van den Heever Department of Atmospheric Science Colorado State University

  2. Differences in TRMM Rainfall Detection February 1, 2000

  3. Impact of Aerosols on Rainfall Detection? TMI-PR Rain Detection Differences SPRINTARS Sulfate AOD

  4. Calipso 532 nm Attenuated Backscatter Aerosol Layer (~3-5 km) Coincident TRMM/CloudSat Case3 April 2007

  5. Coincident TRMM/CloudSat Case3 April 2007

  6. Rain Rate Histograms3 April 2007

  7. Simulated Near-Surface Z Cloud Drizzle Cloud MDS = 18 dBZ Reflectivity (dBZ) PR CPR MDS = -28 dBZ 1 6 10 15 0.1 1 10 100 LWC (gm-3) Rainrate (mm h-1) Differences in Radar SensitivityTRMM PR (13.8 GHz) vs. CloudSat (94 GHz)

  8. Coincident TRMM/CloudSat Case3 April 2007

  9. Cloud Resolving Model SimulationsCSU RAMS Transect of Cloud Liquid Water 3-D Cloud Structure

  10. Total Water Path Cloud Water Path Rain Water Path Cloud Resolving Model SimulationsEffect of Variations in Sulfate Aerosol Optical Depth

  11. Cloud Resolving Model SimulationsEffect of Variations in Sulfate Aerosol Optical Depth Accumulated Precipitation Ratio of Cloud Water Path to Total Water Path

  12. Probability of Precipitation versus Liquid Water Path

  13. Summary • Differences in rain fraction between PR and TMI off the coast of China point to a modification of cloud microphysical properties by aerosols. • Magnitude is substantial (i.e. the frequency of occurrence leads to large differences in the total rain (up to ~50% or 2 mm/day) locally. • Results from 3 April 2007 Case and “Idealized” CRM Simulations • Consistency in rain area between TMI and CloudSat indicate the presence of large-scale light rain and/or drizzle below the PR detection threshold (~17 dBZ) • High AOD CRM simulation has substantially more cloud water and the onset of rain is delayed. • This is consistent with the observations as higher cloud water paths may lead to an overestimate of the rain rate by TMI/CloudSat and possible underestimate by the PR as a result of smaller drops initially. In addition, the delay in the development of rain drops may be a factor leading to the underestimate of the rain area by PR. • Results from Statistical Analysis (Global ocean analysis from 2007) • Probability of precipitation decreases significantly in high sulfate aerosol environment. • Aerosol effect is evident in both stable and unstable environments. • Results are consistent using either SPRINTARS sulfate AOD or MODIS aerosol index.

  14. 500m ~1.4 km The CloudSat Mission Primary Objective: To provide, from space, the first global survey of cloud profiles and cloud physical properties, with seasonal and geographical variations needed to evaluate the way clouds are parameterized in global models, thereby contributing to weather predictions, climate and the cloud-climate feedback problem. • Nadir pointing, 94 GHz radar • 3.3s pulse  500m vertical res. • 1.4 km horizontal res. • Sensitivity ~ -28 dBZ • Dynamic Range: 80 dB • Antenna Diameter: 1.85 m • Mass: 250 kg • Power: 322 W The Cloud Profiling Radar

  15. Tropical Rainfall Measuring Mission (TRMM) TRMM Sensors Nov. 1997 launch, 35° inclination; 402 km Precipitation radar (PR): 13.8 GHz 4.3 km footprint 0.25 km vertical res. 215 km swath Microwave radiometer (TMI): 10.7, 19.3, 21.3, 37.0 85.5 GHz (dual polarized except for 21.3 V-only) 10x7 km FOV at 37 GHz 760 km swath Visible/infrared radiometer (VIRS): 0.63, 1.61, 3.75, 10.8, and 12 : at 2.2 km resolution Lightning Imaging Sensor (LIS ) Cloud & Earth Radiant Energy System (CERES)

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