Atlantic Tropical Studies and airborne sampling strategies

1. Atlantic Tropical Studiesand airborne sampling strategies

2. Advantages of Caribbean Location for Studying Clouds and their interactions with Dust • Tropical maritime convective clouds are less complex to study than convective clouds found over mid latitudes and the continents. They have less day-to-day variations in stability, wind shear, cloud base height, etc. • The Caribbean is subject to regular episodic incursions of dust from Africa, which provides an injection of suspected ice nuclei—an ideal natural experiment to test the effects of dust on the development of precipitation. • The Caribbean provides access to a wide range of tropical clouds of different sizes, including tropical cyclones, an important class of storms for which ice formation is of interest. • The maritime environment of the Caribbean, during non dust events, is similar to many other tropical maritime regions, so the results will have application to our understanding of maritime tropical storms, which are of particular interest to understanding climate. • Tropical convection is less of a concern for aircraft safety. Tropical convection in the temperatures of interest (+5 to -30) is less likely to contain hail or hazardous updrafts and downdrafts that are a major concern for aircraft safety, compared to storms found in mid latitude continental locations. • The RICO project (December—Januray 2004-5) will have provided logistic experience in this area (Antigua).

3. Dust Climatology from Africa is pretty well documented. Monthly mean dust aerosol concentrations at Miami, 1989-1996. From Prospero, J.M., 1999: Long-term measurements of the transport of African mineral dust to the southeastern United States: Implications for regional air quality. JGR Vol 104, No D13, 15917-15927.

4. Some objectives of an ice study in the tropical-subtropical Atlantic • Document microphysical structure of clouds in dusty and non dusty conditions • Follow ice development in tops of growing cu. • Document profiles of liquid water and examine relationship with updraft, entrainment, ice characteristics, temperature, etc. • Evaluate the importance of Rime-Splintering vs primary ice • Fill in missing gaps in Hurricane microphysics

5. Example of possible individual cloud sampling strategy

6. In cloud leg Radar+Lidar Leg In cloud leg Radar+Lidar Leg One-aircraft, example of Radar+ in situ sampling.

7. Strong storms: Sample outer rainbands at various altitudes (-5 to -25 C), working part way towards core Sample weaker, organized regions associated with easterly waves, below hurricane strength. Hurricane Penetrations

8. Possibilities • Share same set of airborne instruments for Atlantic or Pacific Dust/Cloud study • Region of interest is within 1 day of Boulder (e.g. Boulder to Hawaii, or Boulder to Antigua) • Need plume mapping strategy • Tie airborne sampling in with model predictions 24 hrs in advance (flight guidance and model validation) • Possible cross region flight (e.g. Antigua to Cape Verde) with 1 to 3 hours sampling deviation (depending on altitude). Use endpoints or midpoints (e.g. Midway) as possible regions of interest in certain plume conditions.