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2004 NEAQS-ITCT

New England Air Quality - Intercontinental Transport and Chemical Transformation

Ship-Based Measurements of Aerosols Indirect Effects on Cloud Microphysics using a 94-GHz Doppler Radar

The University of Miami UM 94-GHz Doppler Cloud Radar (UMDCR) was deployed on the NOAA research vessel Ronald H. Brown during the Intercontinental Transport and Chemical Transformation (ITCT) and New England Air Quality Study (NEAQS) (July 1- Aug. 15 2004) to characterize cloud microphysics and dynamics of boundary layer clouds. The integration of the UMDCR into the Ronald H. Brown's current instrument suite can considerably improve its capabilities by adding boundary layer cloud observations. The UMDCR cloud reflectivity and the microwave radiometer LWP can be used to derive cloud Liquid Water Content (LWC) and droplet effective radius re which along with the surface aerosol measurements and lidar aerosol backscatter can be used to detect and quantify the aerosol indirect effect. Furthermore, the UMDCR can provide measurements of cloud turbulence and help to investigate the role of turbulence in determining the indirect effect response. For general information about 2004 NEAQS-ITCT, go to the main public 2004 NEAQS-ITCT Website.

Scientific Objectives

Deploying the instruments together produces a synergism that greatly enhances the value of their data and allows for quantification of the Twomey aerosol indirect effect. These observations will help to constrain and evaluate LES derived cloud statistics under various aerosol conditions, highlight the coupling between aerosols, CCN and cloud drop size distribution and assess their role in cloud radiative properties and lifetime.

Observations

The map (Fig. 1) shows the cruise track of the NOAA Research Vessel Ronald H. Brown during the 2004 NEAQS ITCT Project. The ship departed Porstmouth, New Hampshire on July 3 and returned to port August 12. The ship made a scheduled port call in Portsmouth, New Hampshire, from July 23, - July 26. Weekly dates are indicated on the map. The performance of the UMDCR during both legs of the field study was satisfactory. The radar operated on a 24-hour daily base. Overall, radar observations were collected more than 95% of the time the Ronald Brown participated to the field study. Cloud reflectivity; mean Doppler velocity and Doppler spectrum width with a temporal resolution of 2-5 sec and a vertical resolution of 30 m from the surface to 15 km altitude were recorded. The radar was shutdown twice during the first leg during heavy rain events associated with frontal passages. Observations of cloud base and liquid water path (mm) from the ETL ceilometer and ETL microwave radiometer respectively were used to compliment the radar observations. An example of such observations is given in Figure 2, that shows 24 hours of observations of cloud reflectivity (top), ceilometer backscatter and cloud base estimate (middle) and microwave radiometer liquid water path (mm) (bottom).

Cruise track of the NOAA Research Vessel Ronald H. Brown during the 2004 NEAQS ITCT Project.

Figure 1. The ship departed Porstmouth, New Hampshire on July 3 and returned to port August 12. The ship made a scheduled port call in Portsmouth, New Hampshire, from July 23, - July 26. Weekly dates are indicated on the map.

Example of daily data from the UM/ETL container.

Figure 2. The top panel shows cloud reflectivity, ceilometer backscatter and cloud base (middle panel), and LWP (mm) (bottom panel) during 07/15/2004.