Frederick G. Fernald

Bio: Frederick G. Fernald is an academic researcher from University of Denver. The author has contributed to research in topics: Atmospheric lidar & Lidar. The author has an hindex of 1, co-authored 1 publications receiving 1412 citations.

Analysis of atmospheric lidar observations: some comments

Abstract: There have been many discussions of solutions to the lidar equation for elastic scattering (e.g., Fernald et al.,' Klett, 2 Davis, and Collis and Russell ). Most of these are simply variations on Hitschfeld and Bordan's5 solution for meteorological radars. Klett 2 recently restated this solution in a very convenient form for the analysis of lidar observations collected in very turbid atmospheres. His paper has prompted a restatement of the more general solution of Fernald et al.l which is also applicable to mildly turbid atmospheres where both aerosol and molecular scatterers must be considered in the analysis. This has led to a simple numerical scheme for the computer analysis of lidar measurements. The lidar equation for two distinct classes of scatters (Fernald et al.') is

Lidar inversion with variable backscatter/extinction ratios.

Abstract: The conventional approach to solving the single-scattering lidar equation makes use of the assumption of a power law relation between backscatter and extinction with a fixed exponent and constant of proportionality. An alternative formulation is given herein which assumes the proportionality factor in the power law relationship is itself a function of range or extinction. The resulting lidar equation is solvable as before, and examples are given to show how even an approximate description of deviations from the power law form can yield an improved inversion solution for the extinction. A further generalization is given which includes the effects of a background of Rayleigh scatterers.

The CALIPSO Automated Aerosol Classification and Lidar Ratio Selection Algorithm

Abstract: Descriptions are provided of the aerosol classification algorithms and the extinction-to-backscatter ratio (lidar ratio) selection schemes for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) aerosol products One year of CALIPSO level 2 version 2 data are analyzed to assess the veracity of the CALIPSO aerosol-type identification algorithm and generate vertically resolved distributions of aerosol types and their respective optical characteristics To assess the robustness of the algorithm, the interannual variability is analyzed by using a fixed season (June–August) and aerosol type (polluted dust) over two consecutive years (2006 and 2007) The CALIPSO models define six aerosol types: clean continental, clean marine, dust, polluted continental, polluted dust, and smoke, with 532-nm (1064 nm) extinction-to-backscatter ratios Sa of 35 (30), 20 (45), 40 (55), 70 (30), 65 (30), and 70 (40) sr, respectively This paper presents the global distributions of the CALIPSO a

Independent measurement of extinction and backscatter profiles in cirrus clouds by using a combined Raman elastic-backscatter lidar

Abstract: Height profiles of the extinction and the backscatter coefficients in cirrus clouds are determined independently from elastic- and inelastic- (Raman) backscatter signals. An extended error analysis is given. Examples covering the measured range of extinction-to-backscatter ratios (lidar ratios) in ice clouds are presented. Lidar ratios between 5 and 15 sr are usually found. A strong variation between 2 and 20 sr can be observed within one cloud profile. Particle extinction coefficients determined from inelastic-backscatter signals and from elastic-backscatter signals by using the Klett method are compared. The Klett solution of the extinction profile can be highly erroneous if the lidar ratio varies along the measuring range. On the other hand, simple backscatter lidars can provide reliable information about the cloud optical depth and the mean cloud lidar ratio.

Asian dust transported one full circuit around the globe

Abstract: Mineral dust is usually transported long distances in the lower troposphere There are examples of Asian dust being transported across the Pacific Ocean 1‐7 , and traces of Asian dust have also been found in ice and snow cores in Greenland 8 and the French Alps 9 Here, we use measurements from the Cloud‐Aerosol Lidar with Orthogonal Polarization 10 , an air parcel trajectory model and a three-dimensional aerosol transport model to map the transport of dust clouds generated during a storm in China’s Taklimakan Desert during May 2007 We show that the dust-veiled clouds were lofted to the upper troposphere around 8‐10 km above the Earth’s surface and transported more than one full circuit around the globe in about 13 days When the dust reached the northwestern Pacific Ocean for the second time, the subsidence of a large-scale high-pressure system caused it to descend into the lower troposphere; some of the dust was then deposited over the ocean Our analysis also indicates that the dust particles may have acted as ice nuclei in these high-altitude clouds, leading to the formation of cirrus clouds We suggest that Asian dust can influence the global radiation budget by stimulating cirrus cloud formation and marine ecosystems by supplying nutrients to the open ocean The polarization-sensitive Mie lidar is a powerful tool for the measurement of dust aerosols 11 The first long-duration space-borne lidar optimized solely for atmospheric measurements (CloudAerosol

Analysis of a winter regional haze event and its formation mechanism in the North China Plain

Abstract: . A regional haze episode occurred in the Beijing, Tianjin and Hebei province (BTH) area in the North China Plain (NCP) from 16 to 19 January 2010. Data were collected and analyzed during the time frame of 14 through 23 January 2010 to include the haze event. The increase of secondary inorganic pollutants (SO42−, NO3−, NH4+) in PM2.5 was observed simultaneously at four sites, especially in the plain area of the BTH, which could be identified as a common characteristic of pollution haze in east China. The sulfate and nitrate in PM2.5 were mainly formed through the heterogeneous reaction process in the urban area. The organic matter (OM) increased more significantly at the Chengde (CD) site than the other three sites in the plain area. The secondary organic aerosols only existed during haze days at CD but in both haze and non-haze days at the other three sites, which suggested the greater regional impact of secondary formation process during the haze episode. The secondary formation of aerosol was one important formation mechanism of haze. The strong temperature inversion and descending air motions in the planetary boundary layer (PBL) allowed pollutants to accumulate in a shallow layer. The weak surface wind speed produced high pollutants concentration within source regions. The accumulation of pollutants was one main factor in the haze formation. The enhanced southwest wind in the last period of this episode transported pollutants to the downwind area and expanded the regional scope of the haze.