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A New Criterion to Improve Operational Drizzle Detection with Ground-Based Remote Sensingdistributed horizontally and vertically in space. However, drizzle formation can modify cloud water content distributions by removing water content from the cloud; it can also alter in this way the cloud lifetime and the cloud cover, with direct effects on the radiation and also on the thermodynamical structure of the planetary boundary layer (PBL). Drizzle plays a central role in the description of PBL liquid clouds in general circulation models (GCMs). However, drizzle is generally overestimated in GCMs
distributed horizontally and vertically in space. However, drizzle formation can modify cloud water content distributions by removing water content from the cloud; it can also alter in this way the cloud lifetime and the cloud cover, with direct effects on the radiation and also on the thermodynamical structure of the planetary boundary layer (PBL). Drizzle plays a central role in the description of PBL liquid clouds in general circulation models (GCMs). However, drizzle is generally overestimated in GCMs
Separating Cloud and Drizzle Signals in Radar Doppler Spectra Using a Parametric Time Domain Method1. Introduction Boundary layer clouds are fundamental to Earth’s radiation budget due to their vast cloud cover and high albedo ( Hartmann et al. 1992 ; Hahn and Warren 2007 ). They drizzle frequently ( Petty 1995 ; Rémillard et al. 2012 ; Wu et al. 2017 ); the drizzle process not only influences cloud organization and life cycle, but also modulates boundary layer structure and the energy budget ( Wood 2012 ; Ahlgrimm and Forbes 2014 ; Yamaguchi et al. 2017 ; Zhou et al. 2017 ). These
1. Introduction Boundary layer clouds are fundamental to Earth’s radiation budget due to their vast cloud cover and high albedo ( Hartmann et al. 1992 ; Hahn and Warren 2007 ). They drizzle frequently ( Petty 1995 ; Rémillard et al. 2012 ; Wu et al. 2017 ); the drizzle process not only influences cloud organization and life cycle, but also modulates boundary layer structure and the energy budget ( Wood 2012 ; Ahlgrimm and Forbes 2014 ; Yamaguchi et al. 2017 ; Zhou et al. 2017 ). These
1. Introduction Advancing our understanding of the cloud-scale physical processes that affect cloud lifetime requires high-resolution measurements in clouds ( Brenguier and Wood 2009 ). One area of great interest is the separation of cloud and drizzle microphysics and turbulence in warm clouds to shed light on precipitation initiation, including the role of aerosols and dynamics. Aircraft penetrations can provide detailed in situ measurements of these quantities; however, they are expensive
1. Introduction Advancing our understanding of the cloud-scale physical processes that affect cloud lifetime requires high-resolution measurements in clouds ( Brenguier and Wood 2009 ). One area of great interest is the separation of cloud and drizzle microphysics and turbulence in warm clouds to shed light on precipitation initiation, including the role of aerosols and dynamics. Aircraft penetrations can provide detailed in situ measurements of these quantities; however, they are expensive
1. Introduction Drizzle is a form of liquid precipitation that is characterized by “very small, numerous and uniformly dispersed water drops…that fall to the ground…and (are) frequently accompanied by low visibility and fog” ( Huschke 1959 , p. 179). Drizzle has been recognized as a distinct precipitation type since 1806 when Sir Francis Beaufort first developed a system of weather notations designed to facilitate the recording of weather observations ( Heidorn 1998 ). While the human observer
1. Introduction Drizzle is a form of liquid precipitation that is characterized by “very small, numerous and uniformly dispersed water drops…that fall to the ground…and (are) frequently accompanied by low visibility and fog” ( Huschke 1959 , p. 179). Drizzle has been recognized as a distinct precipitation type since 1806 when Sir Francis Beaufort first developed a system of weather notations designed to facilitate the recording of weather observations ( Heidorn 1998 ). While the human observer
Inferring the Presence of Freezing Drizzle Using Archived Data from the Automated Surface Observing System (ASOS)operations. The ASOS provides standard meteorological measurements of temperature, pressure, humidity, wind velocity, sky condition, visibility, obstructions to visibility, and liquid equivalent precipitation accumulation. In its current state, the ASOS can also provide a limited determination of pristine (i.e., non-mixed-phase) precipitation types—namely, rain, snow and freezing rain. Human observers at a limited number of the ASOS stations provide other reported precipitation types, such as drizzle
operations. The ASOS provides standard meteorological measurements of temperature, pressure, humidity, wind velocity, sky condition, visibility, obstructions to visibility, and liquid equivalent precipitation accumulation. In its current state, the ASOS can also provide a limited determination of pristine (i.e., non-mixed-phase) precipitation types—namely, rain, snow and freezing rain. Human observers at a limited number of the ASOS stations provide other reported precipitation types, such as drizzle
1. Introduction Drizzle drops are recognized as having an important effect on global climate by affecting the lifetime of shallow, warm clouds ( Albrecht 1989 ). Accurate measurements are needed for constraining models of precipitation development, and it is often stated that simple models of the growth of drops on aerosol particles cannot explain the shape of observed droplet spectra (e.g., Rogers and Yau 1988 ). This has resulted in many suggestions for how cloud drops may be subject to
1. Introduction Drizzle drops are recognized as having an important effect on global climate by affecting the lifetime of shallow, warm clouds ( Albrecht 1989 ). Accurate measurements are needed for constraining models of precipitation development, and it is often stated that simple models of the growth of drops on aerosol particles cannot explain the shape of observed droplet spectra (e.g., Rogers and Yau 1988 ). This has resulted in many suggestions for how cloud drops may be subject to
properties of these boundary layer clouds in order to explicitly resolve their impact on climate ( Slingo and Slingo 1991 ; O’Connor et al. 2005 ). The purpose of this paper is to describe and evaluate a method for measuring light rain and drizzle drop median equivolumetric size diameter D 0 from collocated MPLNET UV and VIS lidar profiles by taking advantage of the differential backscatter during precipitation at the two wavelengths, respectively. Raindrop size is of particular importance for
properties of these boundary layer clouds in order to explicitly resolve their impact on climate ( Slingo and Slingo 1991 ; O’Connor et al. 2005 ). The purpose of this paper is to describe and evaluate a method for measuring light rain and drizzle drop median equivolumetric size diameter D 0 from collocated MPLNET UV and VIS lidar profiles by taking advantage of the differential backscatter during precipitation at the two wavelengths, respectively. Raindrop size is of particular importance for
1. Introduction Through nearly a decade of studies beginning with the Winter Icing and Storms Projects ( Rasmussen et al. 1992 ), a radar remote sensing capability has been sought to identify ice particles in glaciated and mixed-phase clouds and, specifically, to distinguish clouds of supercooled, 50–500- μ m-diameter, drizzle-sized droplets from clouds of the various ice particles. The wavelength at K a band (8.66 mm) is suitable for detection of these droplets, which are small compared to
1. Introduction Through nearly a decade of studies beginning with the Winter Icing and Storms Projects ( Rasmussen et al. 1992 ), a radar remote sensing capability has been sought to identify ice particles in glaciated and mixed-phase clouds and, specifically, to distinguish clouds of supercooled, 50–500- μ m-diameter, drizzle-sized droplets from clouds of the various ice particles. The wavelength at K a band (8.66 mm) is suitable for detection of these droplets, which are small compared to
direct measurement of airspeed fluctuations ( Meteorology Research, Inc. 1969 ), and this data could be used to estimate an upper bound on the effect turbulence had on the Doppler spectrum measurements. Finally, simulation of the expected Doppler spectrum could be used to establish the impact of sampling on the measured spectra. 7. Description of 14 September case During one period on 14 September 1995, the King Air flew just above the surface (140 m) for about 30 km through light drizzle and a
direct measurement of airspeed fluctuations ( Meteorology Research, Inc. 1969 ), and this data could be used to estimate an upper bound on the effect turbulence had on the Doppler spectrum measurements. Finally, simulation of the expected Doppler spectrum could be used to establish the impact of sampling on the measured spectra. 7. Description of 14 September case During one period on 14 September 1995, the King Air flew just above the surface (140 m) for about 30 km through light drizzle and a
(cumulus, stratocumulus, and stratocumulus with embedded drizzle) are considered and the sampling by the dual-beam radar of RALI, including along-path integrated attenuation (PIA) and realistic noise, is simulated. Finally the two algorithms are applied to the simulated data in order to evaluate their performances in the retrieval of the specific attenuation and true reflectivity fields. Section 6 also discusses the accuracy in the subsequent estimates of cloud liquid water content and effective
(cumulus, stratocumulus, and stratocumulus with embedded drizzle) are considered and the sampling by the dual-beam radar of RALI, including along-path integrated attenuation (PIA) and realistic noise, is simulated. Finally the two algorithms are applied to the simulated data in order to evaluate their performances in the retrieval of the specific attenuation and true reflectivity fields. Section 6 also discusses the accuracy in the subsequent estimates of cloud liquid water content and effective
