Search results for "Water content"
showing 10 items of 380 documents
Arctic low-level boundary layer clouds: in situ measurements and simulations of mono- and bimodal supercooled droplet size distributions at the top l…
2015
Abstract. Aircraft borne optical in situ size distribution measurements were performed within Arctic boundary layer clouds with a special emphasis on the cloud top layer during the VERtical Distribution of Ice in Arctic clouds (VERDI) campaign in April and May 2012. An instrumented Basler BT-67 research aircraft operated out of Inuvik over the Mackenzie River delta and the Beaufort Sea in the Northwest Territories of Canada. Besides the cloud particle and hydrometeor size spectrometers the aircraft was equipped with instrumentation for aerosol, radiation and other parameters. Inside the cloud, droplet size distributions with monomodal shapes were observed for predominantly liquid-phase Arct…
The effects of different radiation parametrizations on cloud evolution
1997
With the use of the microphysical stratus model (MISTRA), investigations into the effects of variations in the radiative-transfer parametrizations on cloud development have been undertaken. Two radiative-transfer schemes were coupled with the microphysical-thermodynamical section of MISTRA, one based on the exponential sumfitting method and the other based on the correlated k-distribution method of determining gaseous absorption properties. Model runs were initiated with parameter values in accordance with measurements made over the North Sea and comparisons made between model runs where only the radiation schemes were altered. Results indicated that differences between the two schemes had …
Comparison of ERA40 cloud top phase with POLDER-1 observations
2008
[1] A detailed grid-point-based comparison of the cloud top phase derived from the 40-year reanalyses (ERA40) of the European Centre for Medium-Range Weather Forecasts (ECMWF) with satellite measurements is presented. For this purpose an algorithm is implemented to extract a two-dimensional “satellite-like” field of the cloud top phase from ERA40 data. This field is compared with cloud top phase data from the Polarization and Directionality of the Earth Reflectances (POLDER-1) instrument which was in orbit from November 1996 to June 1997. The thermodynamic cloud phase in ERA40 data is parameterized as a function of temperature with pure liquid clouds above 0°C, pure ice clouds below −23°C a…
Estimation of the spatially distributed surface energy budget for AgriSAR 2006, part II : Integration of remote sensing and hydrologic modeling
2011
In most hydrologic modeling studies, the hypothesis is made that an improvement in the modeled soil moisture leads to an improvement in the modeled surface energy balance. The objective of this paper is to assess whether this hypothesis is true. The study was performed over the winter wheat fields in the AgriSAR 2006 domain. Remotely sensed soil moisture values and latent heat fluxes were used, in combination with in situ observations. First, the land cover and saturated subsurface flow parameters were estimated using the in situ observations. A spatially distributed model simulation was then performed, for which the Brooks-Corey parameters were derived from a soil texture map, and of which…
Reproducing cloud microphysical and irradiance measurements using three 3D cloud generators
2007
Using three cloud generators, three-dimensional (3D) cloud fields are reproduced from microphysical cloud data measured in situ by aircraft. The generated cloud fields are used as input to a 3D radiative transfer model to calculate the corresponding fields of downward and upward irradiance, which are then compared with airborne and ground-based radiation measurements. One overcast stratocumulus scene and one broken cumulus scene were selected from the European INSPECTRO field experiment, which was held in Norwich, UK, in September 2002. With these data, the characteristics of the three different cloud reproduction techniques are assessed. Besides vertical profiles and histograms of measured…
Effects of 20–100 nm particles on liquid clouds in the clean summertime Arctic
2016
Abstract. Observations addressing effects of aerosol particles on summertime Arctic clouds are limited. An airborne study, carried out during July 2014 from Resolute Bay, Nunavut, Canada, as part of the Canadian NETCARE project, provides a comprehensive in situ look into some effects of aerosol particles on liquid clouds in the clean environment of the Arctic summer. Median cloud droplet number concentrations (CDNC) from 62 cloud samples are 10 cm−3 for low-altitude cloud (clouds topped below 200 m) and 101 cm−3 for higher-altitude cloud (clouds based above 200 m). The lower activation size of aerosol particles is ≤ 50 nm diameter in about 40 % of the cases. Particles as small as 20 nm ac…
Summertime columnar content of atmospheric water vapor from ground-based Sun-sky radiometer measurements through a new in situ procedure
2010
[1] A new in situ technique for the retrieval of atmospheric water vapor content (i.e., precipitable water content) from Sun photometric direct solar irradiance measurements, taken at the 940 nm wavelength during clear‐sky conditions, is presented. The procedure is applied to summer data recorded in 2007, 2008, and 2009 with a Sun‐sky radiometer at the San Pietro Capofiume station in the Po valley, Italy. It is a preliminary development of the retrieval procedure providing the columnar water vapor content from measurements performed with PREDE Sun‐sky radiometers. The technique brings improvement and innovation by retrieving the best values of constants (a and b), characterizing atmospheric…
Influence of soil water content on the thermal infrared emissivity of bare soils. Implication for land surface temperature determination.
2007
[1] The influence of soil water content in thermal infrared emissivity is a known fact but has been poorly studied in the past. A laboratory study for quantifying the dependence of emissivity on soil moisture was carried out. Six samples of surface horizons of different soil types were selected for the experiment. The gravimetric method was chosen for determining the soil moisture, whereas the emissivity was measured at different soil water contents using the two-lid variant of the box method. As a result, the study showed that emissivity increases from 1.7% to 16% when water content becomes higher, especially in sandy soils in the 8.2–9.2 μm range. Accordingly, a set of equations was deriv…
Control of solute concentrations in cloud and fog water by liquid water content
2000
We measured the concentrations of Cl^−, NO_3^−, and SO_4^(2−) in atmospheric cloudwater collected with a passive collector from a remote marine site and the concentrations of Cl^−, NO_3^−, SO_4^(2−), Na^+ and NH_4^+ in cloudwater from a continental site. At the continental site, an active rotating arm collector was employed for cloudwater collection. At both locations, we observed an inverse relationship between the measured ion concentrations and the liquid water content of the clouds. The product of the observed concentrations and the liquid water content, the cloudwater loading, was found to be nearly constant. A study of published cloudwater data showed that at the majority of the exami…
Airborne investigation of the aerosols–cloud interactions in the vicinity and within a marine stratocumulus over the North Sea during EUCAARI (2008)
2013
Abstract Within the European Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) project, the Meteo France research aircraft ATR-42 was operated from Rotterdam (Netherlands) airport during May 2008, to perform scientific flights dedicated to the investigation of aerosol–cloud interactions. The objective of this study is to illustrate the impact of cloud processing on the aerosol particle physical and chemical properties. The presented results are retrieved from measurements during flight operation with two consecutive flights, first from Rotterdam to Newcastle (United Kingdom) and subsequently reverse along the same waypoints back to Rotterdam using data measured with compact Time …