TY - JOUR
T1 - Parameterization of tropical cirrus ice crystal size distributions and implications for radiative transfer
T2 - Results from CEPEX
AU - Mcfarquhar, Greg M.
AU - Heymsfield, Andrew J.
PY - 1997/9/1
Y1 - 1997/9/1
N2 - Average ice crystal size distributions are parameterized as functions of temperature and ice water content (IWD). based on observations in cirrus produced as outflows of deep convection made during the Central Equational Pacific Experiments (CEPEX). as the sum of a first-order gamma function, describing ice crystals with melted equivalent diameters (Dn) less than 100 μm. and a lognormal function, describing larger ice crystals The fit parameters are chosen to minimize the chi-squared function describing the difference between observed and parameterized distribution functions. The parameterization is mass conserving, accurately represents small ice crystals, and is easily integrable. The parameterization given accurate estimates of mass, area, and number contained in different size rangers. The radiative properties estimated from midlatitude parameterizations are compared with those estimated from this parameterization using anomalous diffraction theory. As opposed to some previous studies, small crystals do not dominate the mass and radiative properties of cirrus. Comparison with midlatitude observations shows that size distribution shape can vary substantially depending on where, when, and how the cirrus is measured and on how it forms.
AB - Average ice crystal size distributions are parameterized as functions of temperature and ice water content (IWD). based on observations in cirrus produced as outflows of deep convection made during the Central Equational Pacific Experiments (CEPEX). as the sum of a first-order gamma function, describing ice crystals with melted equivalent diameters (Dn) less than 100 μm. and a lognormal function, describing larger ice crystals The fit parameters are chosen to minimize the chi-squared function describing the difference between observed and parameterized distribution functions. The parameterization is mass conserving, accurately represents small ice crystals, and is easily integrable. The parameterization given accurate estimates of mass, area, and number contained in different size rangers. The radiative properties estimated from midlatitude parameterizations are compared with those estimated from this parameterization using anomalous diffraction theory. As opposed to some previous studies, small crystals do not dominate the mass and radiative properties of cirrus. Comparison with midlatitude observations shows that size distribution shape can vary substantially depending on where, when, and how the cirrus is measured and on how it forms.
UR - http://www.scopus.com/inward/record.url?scp=0000550798&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0000550798&partnerID=8YFLogxK
U2 - 10.1175/1520-0469(1997)054<2187:POTCIC>2.0.CO;2
DO - 10.1175/1520-0469(1997)054<2187:POTCIC>2.0.CO;2
M3 - Article
AN - SCOPUS:0000550798
SN - 0022-4928
VL - 54
SP - 2187
EP - 2200
JO - Journal of the Atmospheric Sciences
JF - Journal of the Atmospheric Sciences
IS - 17
ER -