Abstract Abstract Egyptian Meteorological Authority EMA have 6 upper air stations which used two sounding systems Digicoraiii with Radiotidotite RT 20A ( Vaisala ) and Air sounding system with Radiotidotite (Air) since 2007, so we started at 2007 to new development for two upper air station in (Matrouh and Asswan) from Air sounding system with Radiotidotite (Air) to using Digicoraiii with Radiotidotite RT 20A and GPS wind finding stations and update the software of DigicoraIII in the upper air stations, In this paper the available data of wind has been analyzed and We will show that the loosing of upper wind strong relationship with the seasons by using RDF system so we will explain how to avoid and solve this problems by using new development and operational experience in this paper also, we will use DigicoraIII dual-mode GPS/RDF wind finding data Comparison flights executed in Marsa Matrouh st.during 2006 to 2007 by the EMA. Egyptian Meteorological Authority EMA have 6 upper air stations which used two sounding systems Digicoraiii with Radiotidotite RT 20A ( Vaisala ) and Air sounding system with Radiotidotite (Air) since 2007, so we started at 2007 to new development for two upper air station in (Matrouh and Asswan) from Air sounding system with Radiotidotite (Air) to using Digicoraiii with Radiotidotite RT 20A and GPS wind finding stations and update the software of DigicoraIII in the upper air stations, In this paper the available data of wind has been analyzed and We will show that the loosing of upper wind strong relationship with the seasons by using RDF system so we will explain how to avoid and solve this problems by using new development and operational experience in this paper also, we will use DigicoraIII dual-mode GPS/RDF wind finding data Comparison flights executed in Marsa Matrouh st.during 2006 to 2007 by the EMA. The DigiCORA® Sounding System MW31( Vaisala ) contains The DigiCORA® Sounding System MW31 with the Radiotheodolite RT20A and GPS wind finding ( Vaisala ) contains 1.Radiotheodolite RT20 system :- Radiotheodolite windfinding is best suited for situations where the balloon elevations from the ground station remain high throughout the flight. ie. If the balloon elevations remain above about 16°, At low balloon elevations, the measurement errors with Radiotheodolites increase rapidly with decreasing elevation even with larger tracking aerials It is extremely difficult to satisfy the accuracy, if upper winds are consistently very strong, 2. GPS wind finding system :- portable system with small antennas for 403 MHz telemetry and GPS 0wind finding RS92-SGP Radiosonde for GPS wind Technology, Major Features All-digital code-correlating GPS Radiosonde Higher level of PTU measurement performance Continuously available, highly accurate wind data code correlating GPS. portable system with small antennas for 403 MHz telemetry and GPS 0wind finding RS92-SGP Radiosonde for GPS wind Technology, Major Features All-digital code-correlating GPS Radiosonde Higher level of PTU measurement performance Continuously available, highly accurate wind data code correlating GPS. Vaisala GPS station GPS station Global Positioning System (GPS) GPS Signal Path Egyptian Meteorological Authority (EMA) Koubry ELQuobba EMA, Cairo, Egypt, P. BOX : Fax :

In Egypt their are two kinds of jet stream polar and subtropical jet stream passes in winter and autumn this effects the upper winds are very strong which leads to the balloon elevations at about 13 km altitude remains below 20 degree. At low balloon elevations, the measurement errors with Radiotheodolite wind observations increase rapidly with decreasing Elevation even with larger tracking aerials, It is extremely difficult to satisfy the accuracy if upper winds are very strong, We studied the accuracy of data for upper wind observations at all heights by using ( RDF and GPS ) systems in Matroh station since The period from ( 2006 to 2008 ). from the figures We found that from ( jan to Mar ) the RDF wind observations are smoothed and good accuracy over thick layer at all heights apart from bout 10 km, this layer increasing to about 20 km from ( Oct to Dec), and becomes about 25 km from ( Apr to Sep). Also We found that the GPS wind observations are smoothed over average 25 km altitude. By comparison of wind observations between the two systems RDF and GPS at ( Dec to feb ) we found that the upper wind bservations of GPS system is giving informations of wind at higher altitude than the RDF system, But from ( Apr to Sep ) the information of wind observations have relatively the same value and altitude because this season is summer in Egypt and weak upper wind so the Radiotheodolite wind observations are smoothed and good accuracy until the balloon burst.so we sugested to using GPS system in the period from ( Oct to Mar ) to avoid the loosing of upper wind observations.

TTAA // // ///// // = TTAA // // = Temp message and CLIMAT Application By using S/W Digicoraiii v 2.7 ( Vaisala ) we found the observations which contains measurement errors with Radiotedolite wind observations as the figure. Then we loose the accuracy of data wind observations at all the levels of (core of jet stream ) so this Required many procedures from the operator to truncation errors of wind observations. So When upper winds are reported using either The TEMP AND CLIMATE report By using S/W Digicoraiii v 2.7 ( Vaisala) it should be checked against the detailed upper wind measurement and the reported messages should be edited to eliminate unacceptable fitting errors before issue. but by using new version Digicoraiii v3.52 with RDF or GPS systems their is no errors in upper wind observations so The TEMP AND CLIMATE reports is ok to issue without any modifications. So we obtain the good information of upper wind observations which it is important for weather forecasting at all latitudes, vital to the safety and economy of aircraft operations and important for safety in military operations also.

EMA suggested To development the all upper air stations by dual-mode GPS/RDF system ( Vaisala ). And put programming for using this dual system which using RDF system in the summer and spring and using GPS system in the autumn and winter when there is strong in upper wind over Egypt. But Wind speed and Wind direction are not the same. By statistical method We found the PTU are the same in the two system RDF/ GPS But Wind speed and Wind direction are not the same. From figure (A) we found that the percentage of upper wind observations which not pass to 20 km heights is 33 % in month of Nov, 62 % in Dec, 66 % in Jan,100 % in Feb, 100 % in Mar, 83 % in April but in figure (B) we found that in is period from ( Nov to Mar) the percentage of upper wind observations which not pass to 20 km heights is less than 18 % so we must avoid to using the RDF system in the period of months from ( Nov to Mar). By using RDF system in the period from ( May to Jul ) this percentage is less than 7 % and from ( Aug to Oct ) is less than 30 % so in this period from ( May to Oct ) we can use RDF system. figure (A) figure (B)