VERTICAL MOTION CHARACTERISTICS OF TROPICAL CYCLONES DETERMINED WITH AIRBORNE DOPPLER RADIAL-VELOCITIES

Vertical motions in seven Atlantic hurricanes are determined from data recorded by Doppler radars on research aircraft. The database consist s of Doppler velocities and reflectivities from vertically pointing ra dar rays collected along radial flight legs through the hurricane cent ers. The vertical motions are estimated throughout the depth of the tr oposphere from the Doppler velocities and bulk estimates of particle f allspeeds. Portions of the flight tracks are subjectively divided into eyewall, rainband, stratiform, and ''other'' regions. Characteristics of the vertical velocity and radar structure are described as a funct ion of altitude for the entire dataset and each of the four regions. T n all of the regions, more than 70% of the vertical velocities range f rom -2 to 2 m s(-1). The broadest distribution of vertical motion is i n the eyewall region where similar to 5% of the vertical motions are > 5 m s(-1). Averaged over the entire dataset, the mean vertical velocit y is upward at altitudes. Mean downward motion occurs only in the lowe r troposphere of the stratiform region. Significant vertical variation s in the mean profiles of vertical velocity and reflectivity are discu ssed and related to microphysical processes. In the lower and middle t roposphere, the characteristics of the Doppler-derived vertical motion s are similar to those described in an earlier study using flight-leve l vertical velocities, even though the horizontal resolution of the Do ppler data is similar to 750 m compared to similar to 125 m from the i n situ flight-level measurements. The Doppler data are available at hi gher altitudes than those reached by turboprop aircraft and provide in formation oil vertical as well as horizontal variations. In a vertical plane along the radial flight tracks, Doppler up- and downdrafts are defined at each 300-m altitude interval as vertical Velocities whose a bsolute Values continuously exceed 1.5 m s(-1), with at least one spee d having an absolute value greater than 3.0 m s(-1). The properties of the Doppler drafts are lognormally distributed. In each of the region s, updrafts outnumber downdrafts by at least a factor of 2 and updraft s are wider and stronger than downdrafts. Updrafts in the eyewall slop e radially outward with height and are significantly correlated over l arger radial and vertical extents than in the other three regions. If the downwind (tangential) slope with height of updrafts varies little among the regions, updrafts capable of transporting air with relativel y large moist static energy from the boundary layer to the upper tropo sphere are primarily in the eyewall region. Downdrafts affect a smalle r vertical and horizontal area than updrafts and have no apparent radi al slope. The total upward or downward mass flux is defined as the flu x produced by all of the upward or downward Doppler vertical velocitie s. The maximum upward mass flux in all but the ''other'' region is nea r 1-km altitude, an indication that boundary-layer convergence is effi cient in producing upward motion. Above the sea surface, the downward mass flux decreases with altitude. At every altitude, the total net ma ss flux is upward, except for the lower troposphere in the stratiform region where it is downward. Doppler-derived up- and downdrafts are a subset of the vertical velocity field that occupy small fractions of t he total area, yet they contribute a substantial fraction to the total mass flux, In the eyewall and rainband regions, for example, the Dopp ler updrafts cover less than 30% of the area but are responsible for > 75% and >50% to the total upward mass flux, respectively. The Doppler downdrafts typically encompass less than 10% of the area yet provide s imilar to 50% of the total downward mass flux in the eyewall and simil ar to 20% of the total downward Aux in the rainband, stratiform, and ' 'other'' regions.