On the relationship between relative humidity and particle backscattering coefficient in the marine boundary layer determined with differential absorption lidar

2000 ◽  
Vol 105 (D4) ◽  
pp. 4729-4741 ◽  
Author(s):  
Volker Wulfmeyer ◽  
Graham Feingold
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Marine Boundary Layer ◽  
Differential Absorption ◽  
Backscattering Coefficient ◽  
Differential Absorption Lidar ◽  
Particle Backscattering ◽  
The Relationship

scholarly journals A Revised Conceptual Model of the Tropical Marine Boundary Layer. Part II: Detecting Relative Humidity Layers Using Bragg Scattering from S-Band Radar

2013 ◽  
Vol 70 (10) ◽  
pp. 3025-3046 ◽  
Author(s):  
Jennifer L. Davison ◽  
Robert M. Rauber ◽  
Larry Di Girolamo
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Marine Boundary Layer ◽  
Primary Source ◽  
Vertical Gradient ◽  
Spectral Width ◽  
Bragg Scattering ◽  
Mesoscale Structure ◽  
Close Relationship ◽  
The Relationship

Abstract Persistent layers of enhanced equivalent radar reflectivity factor and reduced spectral width were commonly observed within cloud-free regions of the tropical marine boundary layer (TMBL) with the National Center for Atmospheric Research S-Pol radar during the Rain in Cumulus over the Ocean (RICO) field campaign. Bragg scattering is shown to be the primary source of these layers. Two mechanisms are proposed to explain the Bragg scattering layers (BSLs), the first involving turbulent mixing and the second involving detrainment and evaporation of cloudy air. These mechanisms imply that BSLs should exist in layers with tops (bases) defined by local relative humidity (RH) minima (maxima). The relationship between BSLs and RH is explored. An equation for the vertical gradient of radio refractivity N is derived, and a scale analysis is used to demonstrate the close relationship between vertical RH and N gradients. This is tested using the derived radar BSL boundary altitudes, 131 surface-based soundings, and 34 sets of about six near-coincident, aircraft-released dropsondes. First, dropsonde data are used to quantify the finescale variability of the RH field. Then, within limits imposed by this variability, altitudes of tops (bases) of radar BSLs are shown to agree with altitudes of RH minima (maxima). These findings imply that S-band radars can be used to track the vertical profile of RH variations as a function of time and height, that the vertical RH profile of the TMBL is highly variable over horizontal scales as small as 60 km, and that BSLs are a persistent, coherent feature that delineate aspects of TMBL mesoscale structure.

935 nm Differential Absorption Lidar System and Water Vapor Profiles in Convective Boundary Layer

2017 ◽  
Vol 37 (2) ◽  
pp. 0201003
Author(s):  
洪光烈 Hong Guanglie ◽  
李嘉唐 Li Jiatang ◽  
孔 伟 Kong Wei ◽  
葛 烨 Ge Ye ◽  
舒 嵘 Shu Rong
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Convective Boundary Layer ◽  
Differential Absorption ◽  
Lidar System ◽  
Differential Absorption Lidar ◽  
Convective Boundary

scholarly journals 3D Water Vapor Field in the Atmospheric Boundary Layer Observed with Scanning Differential Absorption Lidar

2016 ◽  
Author(s):  
F. Späth ◽  
A. Behrendt ◽  
S. K. Muppa ◽  
S. Metzendorf ◽  
A. Riede ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Atmospheric Boundary Layer ◽  
Elevation Angle ◽  
Three Dimensions ◽  
Dimensional Structure ◽  
Differential Absorption ◽  
Differential Absorption Lidar ◽  
3 Dimensional ◽  
Western Germany

Abstract. The scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) determines fields of the atmospheric water vapor number density with a temporal resolution of a few seconds and spatial resolution of up to a few tens of meters. We present three case studies which show that this high resolution combined with 2- and 3-dimensional scans allows for new insights in the 3-dimensional structure of the water vapor field in the atmospheric boundary layer (ABL). In spring 2013, the UHOH DIAL was operated within the scope of the HD(CP)2 Observational Prototype Experiment (HOPE) in western Germany. HOPE was part of the project High Definition of Clouds and Precipitation for advancing Climate Prediction (HD(CP)2). Range-height indicator (RHI) scans of the UHOH DIAL show the water vapor heterogeneity within a range of a few kilometers and its impact on the formation of clouds at the ABL top. The uncertainty of the measured data was assessed by extending a technique, which was formerly applied to vertical time series, to scanning data. Typically, even during daytime, the accuracy of the DIAL measurements is between 0.5 and 0.8 g m−3 (or < 6 %) within the ABL, so that now the performance of an RHI scan from the surface to an elevation angle of 90 degrees becomes possible within 10 min. In summer 2014, the UHOH DIAL participated in the Surface-Atmosphere-Boundary-Layer-Exchange (SABLE) campaign in south-western Germany. Volume scans show the water vapor field in three dimensions. In this case, multiple humidity layers were present. Differences in their heights in different directions can be attributed to different surface elevation. With low elevation scans in the surface layer, the humidity profiles and gradients related to different land use and surface stabilities were also revealed.

scholarly journals Time-dependent entrainment of smoke presents an observational challenge for assessing aerosol–cloud interactions over the southeast Atlantic Ocean

2018 ◽  
Vol 18 (19) ◽  
pp. 14623-14636 ◽  
Author(s):  
Michael S. Diamond ◽  
Amie Dobracki ◽  
Steffen Freitag ◽  
Jennifer D. Small Griswold ◽  
Ashley Heikkila ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Atlantic Ocean ◽  
Marine Boundary Layer ◽  
Climate Modeling ◽  
Cloud Droplet ◽  
Number Concentration ◽  
Cloud Properties ◽  
History Of ◽  
Cloud Droplet Number Concentration ◽  
The Relationship

Abstract. The colocation of clouds and smoke over the southeast Atlantic Ocean during the southern African biomass burning season has numerous radiative implications, including microphysical modulation of the clouds if smoke is entrained into the marine boundary layer. NASA's ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign is studying this system with aircraft in three field deployments between 2016 and 2018. Results from ORACLES-2016 show that the relationship between cloud droplet number concentration and smoke below cloud is consistent with previously reported values, whereas cloud droplet number concentration is only weakly associated with smoke immediately above cloud at the time of observation. By combining field observations, regional chemistry–climate modeling, and theoretical boundary layer aerosol budget equations, we show that the history of smoke entrainment (which has a characteristic mixing timescale on the order of days) helps explain variations in cloud properties for similar instantaneous above-cloud smoke environments. Precipitation processes can obscure the relationship between above-cloud smoke and cloud properties in parts of the southeast Atlantic, but marine boundary layer carbon monoxide concentrations for two case study flights suggest that smoke entrainment history drove the observed differences in cloud properties for those days. A Lagrangian framework following the clouds and accounting for the history of smoke entrainment and precipitation is likely necessary for quantitatively studying this system; an Eulerian framework (e.g., instantaneous correlation of A-train satellite observations) is unlikely to capture the true extent of smoke–cloud interaction in the southeast Atlantic.

scholarly journals Measurements and modelling of molecular iodine emissions, transport and photodestruction in the coastal region around Roscoff

2010 ◽  
Vol 10 (23) ◽  
pp. 11823-11838 ◽  
Author(s):  
R. J. Leigh ◽  
S. M. Ball ◽  
J. Whitehead ◽  
C. Leblanc ◽  
A. J. L. Shillings ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Coastal Region ◽  
Molecular Iodine ◽  
Transport Processes ◽  
Optical Absorption Spectroscopy ◽  
Emission Rates ◽  
Cavity Ringdown Spectroscopy ◽  
The Relationship

Abstract. Iodine emissions from the dominant six macroalgal species in the coastal regions around Roscoff, France, have been modelled to support the Reactive Halogens in the Marine Boundary Layer Experiment (RHaMBLe) undertaken in September 2006. A two-dimensional model is used to explore the relationship between geographically resolved regional emissions (based on maps of seaweed beds in the area and seaweed I2 emission rates previously measured in the laboratory) and in situ point and line measurements of I2 performed respectively by a broadband cavity ringdown spectroscopy (BBCRDS) instrument sited on the shoreline and a long-path differential optical absorption spectroscopy (LP-DOAS) instrument sampling over an extended light path to an off-shore island. The modelled point and line I2 concentrations compare quantitatively with BBCRDS and LP-DOAS measurements, and provide a link between emission fields and the different measurement geometries used to quantify atmospheric I2 concentrations during RHaMBLe. Total I2 emissions over the 100 km2 region around Roscoff are calculated to be 1.7×1019 molecules per second during the lowest tides. During the night, the model replicates I2 concentrations up to 50 pptv measured along the LP-DOAS instrument's line of sight, and predicts spikes of several hundred pptv in certain conditions. Point I2 concentrations up to 50 pptv are also calculated at the measurement site, in broad agreement with the BBCRDS observations. Daytime measured concentrations of I2 at the site correlate with modelled production and transport processes. However substantial recycling of the photodissociated I2 is required for the model to quantitatively match measured concentrations. This result corroborates previous modelling of iodine and NOx chemistry in the semi-polluted marine boundary layer which proposed a mechanism for recycling I2 via the formation, transport and subsequent reactions of the IONO2 reservoir compound. The methodology presented in this paper provides a tool for linking spatially distinct measurements to inhomogeneous and temporally varying emission fields.

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