We propose to join the CALIPSO science team. We request funding to perform four tasks.
First, we will use CALIPSO data to identify the location of polar stratospheric clouds (PSCs), and to categorize them. We will compare these data with POAM, HIRDLS and other data. We will then use this data to test and develop a numerical model for PSCs that we are constructing using the NCAR WACCM model. Our simulations use analyzed winds, so we will make one-to-one comparisons with the actual data for the time period of the observations, rather than doing climatologically comparisons. This work will help us make more realistic PSC models for use in ozone chemistry codes. It will help us test algorithms that distinguish PSC types. It will aid in three-dimensional visualization of the PSC fields and stratospheric aerosols.
Our second task will be to use CALIPSO data to identify nitric acid particles in tropical stratospheric clouds (TSCs). These clouds can be separated from sub-visible cirrus by particle size (wavelength dependent backscatter). This work will help us identify where these clouds form and improve our models of them. We will explore the importance of nitric acid condensation to the nitric acid fields in the stratosphere and upper troposphere in the tropics using Aura data on nitric acid coupled with CALIPSO data on clouds. We will model the ways in which clouds alter the nitric acid abundance. Using a three-dimensional model of tropical cirrus clouds, we will simulate the nitric acid abundance in the tropical tropopause transition layer (TTL) and explore where nitric acid should be impacted by clouds and how this relates to water vapor transport.
Our third task will be to use lidar data to characterize the properties of tropospheric aerosols. The lidar data should provide unprecedented insight into the heights of aerosol layers, and constrain aerosol opacity over wide areas. We will use CALIPSO data to constrain the altitudes of smoke clouds from fires. The injection altitudes are poorly known, but greatly influence the long-range transport of smoke. Our goal will be to develop a database, from which we can develop a physical model of the plume rise. We expect the plume rise to depend on fire intensity, and on meteorological parameters that determine the heights of cumulus. We will use the CALIPSO data to constrain our modeling of the global scale transport of aerosols, especially smoke, and their impact on climate.
Finally, we will perform laboratory studies to support CALIPSO. One goal is to better understand the backscatter from ice clouds. The backscatter from large ice crystals should be wavelength independent. CALIPSO plans to use the neutral scattering by clouds for its calibration. However, lidar data from field campaigns indicate the near infrared backscatter can be only 80% of its value in the visible. Possibly this data indicates small particles are present at cloud top. Perhaps it indicates that non-spherical ice particles have surprising optical behavior. We propose to measure both the extinction and backscatter from ice crystals in the lab to determine if there is unexpected wavelength dependent scattering and what causes it. We will also measure the scattering properties of NAT and NAD, which cannot be calculated, so that PSC properties may be retrieved from CALIPSO data. Our second laboratory project is to determine how solid PSCs and TSCs form. This is a critical unresolved issue for denitrification. CALIPSO is likely to shed light on when and where solid PSC particles occur. We will make laboratory measurements to confirm how nucleation occurs.
