6 research outputs found
Overview of microphysical and state parameter measurements from FIRE 2
In this article we present data collected by the NCAR King Air and Sabreliner aircraft in the FIRE 2 cirrus project over southeastern Kansas and northeastern Oklahoma in Nov. and Dec. of 1991. We present state parameter and microphysical measurements in summary form for the dates which have been selected by the FIRE Science Team for intensive analysis, 25 and 26 Nov. and 5 and 6 Dec. We will also evaluate the performance of 'key' aircraft instrumentation
Recommended from our members
Upper-tropospheric relative humidity observation and implications for cirrus ice nucleation
Relative humidity (RH) measurements acquired in orographic wave cloud and cirrus environments are used to investigate the temperatureâdependent RH required to nucleate ice crystals in the upper troposphere, RHnuc(T). High iceâsupersaturations in clear airâconducive to the maintenance of aircraft contrails yet below RHnuc and therefore insufficient for cirrus formationâare not uncommon. Earlier findings are supported that RHnuc in midâlatitude, continental environments decreases from waterâsaturation at temperatures above â39°C to 75% RH at â55°C. Uncertainty in determining RHnuc below â55°C results in part from size detection limitations of the microphysical instrumentation, but analysis of data from the SUCCESS experiment indicates that RHnuc below â55°C is between 70 and 88%. A small amount of data acquired offâshore suggests the possibility that RHnuc may also depend on properties of the aerosols
Evidence for the Predominance of Mid-Tropospheric Aerosols as Subtropical Anvil Cloud Nuclei
NASA's recent Cirrus Regional Study of Tropical Anvils and Cirrus LayersâFlorida Area Cirrus Experiment focused on anvil cirrus clouds, an important but poorly understood element of our climate system. The data obtained included the first comprehensive measurements of aerosols and cloud particles throughout the atmospheric column during the evolution of multiple deep convective storm systems. Coupling these new measurements with detailed cloud simulations that resolve the size distributions of aerosols and cloud particles, we found several lines of evidence indicating that most anvil crystals form on mid-tropospheric rather than boundary-layer aerosols. This result defies conventional wisdom and suggests that distant pollution sources may have a greater effect on anvil clouds than do local sources
Recommended from our members
An analysis of satellite, radiosonde, and lidar observations of upper tropospheric water vapor from the Atmospheric Radiation Measurement Program
To improve our understanding of the distribution and radiative effects of water vapor, the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Program has conducted a series of coordinated water vapor Intensive Observation Periods (IOPs). This study uses observations collected from four ARM IOPs to accomplish two goals: First we compare radiosonde and Raman lidar observations of upper tropospheric water vapor with colocated geostationary satellite radiances at 6.7 ÎŒm. During all four IOPs we find excellent agreement between the satellite and Raman lidar observations of upper tropospheric humidity with systematic differences of âŒ10%. In contrast, radiosondes equipped with Vaisala sensors are shown to be systematically drier in the upper troposphere by âŒ40% relative to both the lidar and satellite measurements. Second, we assess the performance of various âcorrectionâ strategies designed to rectify known deficiencies in the radiosonde measurements. It is shown that existing methods for correcting the radiosonde dry bias, while effective in the lower troposphere, offer little improvement in the upper troposphere. An alternative method based on variational assimilation of satellite radiances is presented and, when applied to the radiosonde measurements, is shown to significantly improve their agreement with coincident Raman lidar observations. It is suggested that a similar strategy could be used to improve the quality of the global historical record of radiosonde water vapor observations during the satellite era