Difficulties in early ice detection with the Small Ice Detector 2 HIAPER (SID-2H) in maritime cumuli

© Copyright 2014 American Meteorological Society (AMS).The Small Ice Detector 2 HIAPER (SID-2H) was used to attempt to detect small ice particles in the early stages of ice formation in the high liquid water environment of tropical maritime cumulus clouds sampled during the Ice in Clouds Experiment - Tropical (ICE-T) field campaign. Its performance in comparison to other probes, and the development of new corrections applied to the data, are presented. The SID-2H detected small ice crystals among larger particles. It correctly identified water drops, and discriminated between round and irregular particle shapes in water-dominated clouds with errors less than 5%. Remaining uncertainties in the sensing volume, and the volume over which coincidence of particles occurred, result in the data being used here in a qualitative manner to identify the presence of ice, its habits and sizes.Peer reviewe

The effects of climate change on hailstorms

Hailstorms are dangerous and costly phenomena that are expected to change in response to a warming climate. In this Review, we summarize current knowledge of climate change effects on hailstorms. As a result of anthropogenic warming, it is generally anticipated that low-level moisture and convective instability will increase, raising hailstorm likelihood and enabling the formation of larger hailstones; the melting height will rise, enhancing hail melt and increasing the average size of surviving hailstones; and vertical wind shear will decrease overall, with limited influence on the overall hailstorm activity, owing to a predominance of other factors. Given geographic differences and offsetting interactions in these projected environmental changes, there is spatial heterogeneity in hailstorm responses. Observations and modelling lead to the general expectation that hailstorm frequency will increase in Australia and Europe, but decrease in East Asia and North America, while hail severity will increase in most regions. However, these projected changes show marked spatial and temporal variability. Owing to a dearth of long-term observations, as well as incomplete process understanding and limited convection-permitting modelling studies, current and future climate change effects on hailstorms remain highly uncertain. Future studies should focus on detailed processes and account for non-stationarities in proxy relationships

2016 Lasher-Trapp Blue Waters Professor Report

2016 annual report for Sonia Lasher-Trapp Blue Waters Professor allocation.NSF OCI-0725070NSF ACI-1238993Ope

2018 Lasher-Trapp Blue Waters Professor Report

2018 annual report for Sonia Lasher-Trapp Blue Waters Professor allocationNSF OCI-0725070NSF ACI-1238993Ope

Ultragiant aerosol growth by collection within a warm continental cumulus congestus.

Results suggest that UGA are only marginally important for warm rain formation in a short-lived cloud such as that studied here. Although the cloud has a very high liquid water content \rm ({>} 5\ g\ m\sp{-3}) and the maximum observed number of UGA are used, raindrop production is low \rm ({\sim}300\ m\sp{-3} maximum concentration). No drop recirculation or breakup processes enhance the production of rain in the modeled iv cloud, because the cloud lifetime is very short. Although little rain is produced in the modeled cloud, the reflectivity factor reaches 40 dBZ within 12 minutes, demonstrating the danger in using the radar echo alone to define significant amounts of rain, particularly when UGA are present in the cloud.The nested-grid version of the Straka Atmospheric Model is used to simulate the three-dimensional wind and cloud water fields at a spatial resolution of 50 m. Within the simulated fields, "packets" of UGA are released at cloud base and grow in a Lagrangian framework by continuous collection. A history of radar reflectivity factor, as well as drop size spectra and trajectory information, is produced.The present study models the growth of UGA by collection within a cloud observed during the Small Cumulus Microphysics Study (SCMS). The observed cloud grew within a continental air mass (cloud base drop concentration \rm {\sim}600\ cm\sp{-3}), reached a depth of 4.5 km and produced a 10 dBZ radar echo within 12 minutes.Ultragiant aerosol (UGA) have been proposed as important initiators of coalescence in warm cumuli. When these particles are ingested at cloud base, they can immediately collect the smaller cloud droplets, thereby reducing the time needed to initiate coalescence in the cloud. Observational studies have documented the existence of UGA near the ground at concentrations greater than 1000 \rm m\sp{-3}, decreasing, with altitude. Whether or not these UGA concentrations are large enough to affect warm rain formation has been the subject of long-standing debate. Past modeling studies have been limited by one-dimensional treatments and inadequate observational data with which to compare the results

The minor importance of giant aerosol to precipitation development within small trade wind cumuli observed during RICO

The present study examines the importance of giant aerosol to precipitation development in marine trade wind cumuli with a new analysis method of a new extensive dataset collected during the Rain in Cumulus over the Ocean (RICO) field campaign. Giant aerosol particles were quantified from clear-air aircraft data, and the precipitation development in the clouds was tracked with dual-polarization radar data. For six different days and multiple clouds on each day, the evolution of the maximum reflectivity, and its associated differential reflectivity, was analyzed. These data were compared with the results of microphysical calculations run within an adiabatic parcel model initialized with the environmental conditions and giant aerosol concentrations on each day of interest. Despite all clouds having formed in a similar maritime environment, this study found substantial variability in the radar echo development both in clouds observed during the same day, and across other days. The maximum reflectivity attained by the clouds appeared to be largely a function of their depth. The radar echo evolution could be represented fairly well by the microphysical parcel model initialized with the observed giant aerosol in some cases but not others. The importance of the giant aerosol to precipitation formation in the small trade wind cumuli appears to be minor: the early radar echoes appear to be more consistent with the development of precipitation by collision and coalescence among droplets formed on the more numerous and smaller cloud condensation nuclei, although the number of giant aerosol appears to have some effect on the actual radar reflectivity values

The effects of climate change on hailstorms

Hailstorms are dangerous and costly phenomena that are expected to change in response to a warming climate. In this Review, we summarize current knowledge of climate change effects on hailstorms. As a result of anthropogenic warming, it is generally anticipated that low-level moisture and convective instability will increase, raising hailstorm likelihood and enabling the formation of larger hailstones; the melting height will rise, enhancing hail melt and increasing the average size of surviving hailstones; and vertical wind shear will decrease overall, with limited influence on the overall hailstorm activity, owing to a predominance of other factors. Given geographic differences and offsetting interactions in these projected environmental changes, there is spatial heterogeneity in hailstorm responses. Observations and modelling lead to the general expectation that hailstorm frequency will increase in Australia and Europe, but decrease in East Asia and North America, while hail severity will increase in most regions. However, these projected changes show marked spatial and temporal variability. Owing to a dearth of long-term observations, as well as incomplete process understanding and limited convection-permitting modelling studies, current and future climate change effects on hailstorms remain highly uncertain. Future studies should focus on detailed processes and account for non-stationarities in proxy relationships