{"id":891,"date":"2019-07-09T14:15:12","date_gmt":"2019-07-09T13:15:12","guid":{"rendered":"http:\/\/35.193.178.118\/?page_id=198"},"modified":"2019-11-08T11:10:55","modified_gmt":"2019-11-08T11:10:55","slug":"mviri-fcdr","status":"publish","type":"page","link":"https:\/\/research.reading.ac.uk\/fiduceo\/fcdrs\/fcdr-case-studies\/mviri-fcdr\/","title":{"rendered":"MVIRI FCDR"},"content":{"rendered":"\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n

The visible channel of the Geostationary MVIRI instrument needed some special care to be fit for climate studies. Here is how we approached the Problem.<\/p>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n

\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n

The Measurements<\/h2>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
\r\n
\r\n
\r\n
\u00a0<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n

MVIRI\u2019s channel for visible light measures a broad band of wavelengths roughly between 0.4 and 1.0 \u00b5m. Covering the blue, green and red spectral regions at once, the images, that are obtained every 30 minutes, are essentially grey (Figure 1): Dark surfaces, such as oceans, appear dark and bright surfaces, such as deserts or clouds, appear bright. Despite the lack of color, a series of seven MVIRI Instruments now has served the weather community for 35 years with valuable information on the state of the atmosphere (eg. cloud fraction) and surface (solar irradiation, surface albedo). The image pixel received from the satellites are dimensionless counts, but they can be transformed into top-of the atmosphere reflectance by applying the measurement equation, which includes the application of the calibration:<\/p>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n\r\n\\rho = \\frac{\\pi \\textcolor{black}{d}^2 }\r\n{\\textcolor{black}{\\tilde{E}_{0,sun}}cos(\\textcolor{black}{\\theta})}\r\n[(\\textcolor{black}{\\overline {C}_{E}}-\\textcolor{black}{\\overline {C}_{S}})\r\n(a_{0}+a_{1}\\textcolor{black}{Y}_t+a_{2}\\textcolor{black}{Y}_t +0)]\r\n<\/span>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n

\r\n
\r\n