On the regional climatic impact of contrails: microphysical and radiative properties of contrails and natural cirrus clouds

International audienceThe impact of contrail-induced cirrus clouds on regional climate is estimated for mean atmospheric conditions of southern Germany in the months of July and October. This is done by use of a regionalized one-dimensional radiative convective model (RCM). The influence of an increased ice cloud cover is studied by comparing RCM results representing climatological values with a modified case. In order to study the sensitivity of this effect on the radiative characteristics of the ice cloud, two types of additional ice clouds were modelled: cirrus and contrails, the latter cloud type containing a higher number of smaller and less of the larger cloud particles. Ice cloud parameters are calculated on the basis of a particle size distribution which covers the range from 2 to 2000 µm, taking into consideration recent measurements which show a remarkable amount of particles smaller than 20 µm. It turns out that a 10% increase in ice cloud cover leads to a surface temperature increase in the order of 1K, ranging from 1.1 to 1.2K in July and from 0.8 to 0.9K in October depending on the radiative characteristics of the air-traffic-induced ice clouds. Modelling the current contrail cloud cover which is near 0.5% over Europe yields a surface temperature increase in the order of 0.05K

Detection of polar stratospheric clouds with ERS-2/GOME data

Based on radiative transfer calculations, it is studied whether polar stratospheric clouds (PSCs) can be detected by the new Global Ozone Monitoring Experiment (GOME) on board the second European Research Satellite (ERS-2) planned to be launched in 1995. It is proposed to identify PSC-covered areas by use of an indicator, the Normalized Radiance Difference (NRD), which relates the difference of two spectral radiances at 0.515 µm and 0.67 µm to one radiance measured in the centre of the oxygen A-band at 0.76 µm. Simulations are carried out for two solar zenith angles, θ=78.5° and θ=86.2°. They indicate that, in presence of PSCs and with increasing solar zenith angles above θ=80°, the NRD decrease to values clearly below those derived under conditions of a cloud-free stratosphere. Results for θ=86.2° show that the method is successful independent of existing tropospheric clouds, of different tropospheric aerosol loadings, and of surface albedos. Results for θ=78.5° illustrate that PSC detection under conditions of smaller solar zenith angles θ80° needs additional information about tropospheric clouds

On the regional climatic impact of contrails: microphysical and radiative properties of contrails and natural cirrus clouds

The impact of contrail-induced cirrus clouds on regional climate is estimated for mean atmospheric conditions of southern Germany in the months of July and October. This is done by use of a regionalized one-dimensional radiative convective model (RCM). The influence of an increased ice cloud cover is studied by comparing RCM results representing climatological values with a modified case. In order to study the sensitivity of this effect on the radiative characteristics of the ice cloud, two types of additional ice clouds were modelled: cirrus and contrails, the latter cloud type containing a higher number of smaller and less of the larger cloud particles. Ice cloud parameters are calculated on the basis of a particle size distribution which covers the range from 2 to 2000 µm, taking into consideration recent measurements which show a remarkable amount of particles smaller than 20 µm. It turns out that a 10% increase in ice cloud cover leads to a surface temperature increase in the order of 1K, ranging from 1.1 to 1.2K in July and from 0.8 to 0.9K in October depending on the radiative characteristics of the air-traffic-induced ice clouds. Modelling the current contrail cloud cover which is near 0.5% over Europe yields a surface temperature increase in the order of 0.05K

The Impact of UVR and Climate Conditions on Fish Stocks: A Case Study of the Northeast Arctic Cod - (UVAC)

2 pages.-- European Conference on Marine Science & Ocean Technology, Celebrating European Marine Science, Building the European Research Area, Communicating Marine Science, Galway, Ireland, 10–13 May 2004N

Three-dimensional cloud effects and satellite UV mapping

Satellite UV mapping is usually based on the independent pixel approximation (IPA) which means that 3-dimensional radiative interaction processes are not taken into account. Especially the inhomogeneity of cloud fields causes uncertainties in the derived UV radiation fields. By comparing results of 1D and 3D UV radiative transfer calculations for three different cloud scenes which are selected to represent a broad range of cloud inhomogeneity the main 3D cloud effects are identified and quantified. With respect to the different spatial resolutions of satellite instruments it is further shown how 3D cloud effects average out with increasing spatial scale. Analysing the ratios relating the results of 1D and 3D radiative transfer calculations it turns out that IPA may produce maximum uncertainties locally up to #+-#100% for a spatial resolution of about 1 x 1 km"2, they are reduced to #+-#10% for a resolution of about 15 x 15 km"2. (orig.)20 refs.Available from TIB Hannover: RR 6341(127) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Monitoring surface UV-B from ERS-2/GOME and NOAA/AVHRR data

A satellite based method for deriving spatial distributions of the UV-B radiation at the surface has been developed. The effects of ozone column amount and cloud optical thickness on UV-B were taken into account by the combined usage of the new European-space-agency's GOME (global-ozone-monitoring-experiment) sensor onboard the European-research-satellite-2 (ERS-2) and the NOAA/AVHRR instrument, respectively. As an example for application, horizontal distributions of surface UV-B flux densities are derived in a region covering the area of Southern Germany on two days 22. July and 13. August 1996. These two days represent clear and cloudy conditions, respectively. Comparisons of satellite deduced UV-B flux densities to local surface UV-B measurements at Hohenpeissenberg (Southern Germany) agree by 7.8% for the clear sky case on 22. July 1996. In addition, the accuracy of the method in case of cloudy conditions is discussed. (orig.)17 refs.Available from TIB Hannover: RR 6341(72) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman