The YYYYMM000000-ESACCI-L3C_AEROSOL-AER-GOMOS_ENVISAT-AERGOM_MONTHLY-fv2.1nc files contain the binned stratospheric aerosols properties derived from the AerGom algorithm using GOMOS v601 data. - AOD and extinction are now given at 550nm - PSCs have been filtered based on PSC I(NAT) formation temperature - Angstrom coefficient for extinction and AOD [400 - 800]nm - cirrus clouds are currently not filtered. CHANGES ------------ *11.06.2013* Files version 2.1 contain data produced by the AerGom algorithm. New variables have also been added to the netCDF files including "Number of Observations" for the extinction and the AOD, as well as the PSC occurrence frequency. *29.10.2012* Files version 2.02 fixes some problems with the naming convention and some netCDF global attributes ('project' is no more absent and the institution has been updated). *01.07.2012* Files version 2.01 now follow the guidelines concerning the naming conventions, as currently agreed upon by the Aerosol_CCI consortium. *01.05.2012* The new version (2.0) of the dataset reflects the use of the long-awaited GOMOS data v6.01 as an input for the AERGOM retrieval. This permits the retrieval of the AOD and extinction at 550nm (compared to 500nm before). Because the new data allows a retrieval of the extinction/AOD at various wavelengths, this information is used do derive the Angstrom coefficient, both for the extinction and the AOD. The Angstrom coefficient is computed using a least-square fit on a log/log plot of the extinction and wavelength between 400 and 756nm, inclusively. As before, the PSCs have been filtered based on PSCI(NAT) formation temperature. The AOD is calculated by integrating the extinction between tropopause height+2km to 50km. The tropopause height calculation has been improved, using the dynamical tropopause at mid- and high-latitudes and thermal tropopause elsewhere. A bug has also been fixed in the thermal tropopause calculation, which will probably improve the validation with CALIPSO. Another change to the data is the error calculation of the AOD and extinction, which is now simply computed as the (geophysical) standard deviation of the P25-P75 data throughout the month. This will be a better reflection of the state of our knowledge of the data, rather than the error of the monthly mean. The data vertical grid is now finer, with a 0.5km increment. There is no filtering of cirrus clouds, but they should not contribute to the AOD either assuming that the tropopause height is accurate. *29.08.2011* In addition to the data already present in the v1.0 of the product, two additional variables have been added to the file: - Cirrus_fraction - PSC_fraction In the case of GOMOS, the cloud coverage should be understood at the number of cirrus clouds/PSC clouds detection divided by the total amount of observations, in a given bin during the month. These variables are to be used with care since they are not very precise, nor have they been verified. They are provided as indication only. > The PSC detection is currently not based on any GOMOS measurements but on the comparison of PSC I(NAT) formation temperature and ECMWF data. > The cirrus detection is based on a purely empirical and arbitrary approach, probably not very accurate: if the extinction in the lower portion of the atmosphere (0-20km) reaches values equal or larger than 25E-3 km-1, the profile is assumed to contain a cirrus clouds. *06.06.2011* The files have been updated so that the array dimensions follow the guidelines of Aerosol_CCI, namely that the arrays are in [lat, lon] format, and not the contrary. The 3-dimensional variables have also been changed so that their dimensions now have the format [lat,lon,alt]. Some errors in the data representation shave been fixed.