Abstract
For synoptic-scale motions the vertical velocity component is typically of the order of a few centimeters per second. In general, the vertical velocity is not measured directly but must be inferred from other meteorological fields that are measured directly. In the present study, a Joss–Waldvogel disdrometer was used in order to establish the drop size distributions (DSD) at Athalassa, Cyprus. Data from a radiosonde station co-located with the disdrometer were also collected which were subsequently used to derive estimates of vertical velocities. Meteorological fields, including vertical velocities, were extracted from an atmospheric reanalysis, for an area centered over the disdrometer and radiosonde station instrumentation. The disdrometer data were used to determine the Z-R disdrometer derived coefficients, A and b, where Z = A Rb. To model the vertical air effect on the Z-R disdrometer derived coefficients an idealistic notion of flux conservation of the DSD is adopted. This adjusted DSD (FCM-DSD) is based on the exponential DSD and is modified by the relationship between drop terminal velocity (D) and vertical air speed w . The FCM-DSD has a similar appearance to the popular gamma DSD for w < 0. A clear segregation is seen in the A-w plane for both data and model. The data points are also clearly segregated in the b- w plane, but the model points are on opposite sides of the w = 0 line. It is also demonstrated that vertical velocities can be extracted from radiosonde data if initial balloon volume is accurately measured, along with an accurate measurement of the mass of the complete radiosonde-balloon system. To accomplish this, vertical velocities from radiosonde data were compared to reanalysis vertical velocity fields. The resulting values of initial balloon volume are found to be within the range of measured values.
Highlights
One meteorological variable which has a profound effect on the weather is the vertical velocity of the atmospheric air [1,2,3]
The flux conservation model (FCM)-drop size distributions (DSD) has a similar appearance to the popular gamma DSD for w < 0
To understand how flux conservation model (FCM) will lead to a change in the DSD spectra, refer to Figure 4, where a DSD described by N ( D ) is falling with a combined terminal velocity v( D ) and vertical air motion w (see Equations (27) and (28) in Lane et al [21])
Summary
One meteorological variable which has a profound effect on the weather is the vertical velocity of the atmospheric air (hereafter denoted by w, in m s−1 ) [1,2,3]. Through sustained vertical motions, rising moist air cools adiabatically forming precipitating cloud [4], sometimes accompanied with more notable phenomena, like lightning and thunder [1]. Rising motions can lead to a steeper environmental temperature lapse rate [5] and strengthening of cyclonic systems [1,3]. On the contrary, descending air is heated by diabatic compression leading to cloud dissipation, damping of precipitation, clearer skies, and finer weather. Bearing in mind the importance of vertical motions in the atmosphere, this study presents the methodology and results of an attempt to deduce information about the character of the Atmosphere 2019, 10, 77; doi:10.3390/atmos10020077 www.mdpi.com/journal/atmosphere. Atmosphere 2019, 10, 77 vertical air motion adopting a methodology that combines measurements from three data sources: a. For scales of motion in the Earth’s atmosphere with horizontal dimensions exceeding 100 km, the (horizontal) length scale significantly exceeds the depth (vertical) scale; most importantly and in connection to the focus of this paper, typical magnitudes of the horizontal velocity component exceed those of the vertical velocity component by several orders of magnitude [1,2], except in very strong convection currents where horizontal and vertical velocities attain comparable values (see [2])
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