How to download JRA-55 datasets?
1 Introduction / JRA-55數(shù)據(jù)集介紹
? The Japan Meteorological Agency (JMA) carried out the second reanalysis project (known as the Japanese 55-year Reanalysis, or JRA-55) using a more sophisticated DA system based on the operational system as of December 2009, and newly prepared dataset of past observations. The analysis period covers the 55 years from 1958, when regular radiosonde observation began on a global basis. Many of the deficiencies of JRA-25 are alleviated in JRA-55 because the DA system used for the project featured a variety of improvements introduced after JRA-25. As a result, the JRA-55 project produced a high-quality homogeneous climate dataset covering the last half century.
2 Preparation / 準(zhǔn)備工作
Linux系統(tǒng)或虛擬環(huán)境，安裝Python2或Python3，并檢查是否有requests庫(kù)，命令如下：
3 Detailed steps / 具體步驟
以在NCAR RDA官方頁(yè)面下載月平均數(shù)據(jù)集為例，無(wú)需注冊(cè)賬號(hào)。
(1)?NCAR RDA中JRA-55月平均數(shù)據(jù)鏈接為https://rda.ucar.edu/datasets/ds628.1/。
(2)?在DATA ACCRSS欄下，有各種JRA55月平均和方差數(shù)據(jù)，常用的包括等壓面分析場(chǎng)(isobaric analysis fields)和地表分析場(chǎng)(surface analysis fields)等。選擇需要的數(shù)據(jù)，進(jìn)入Web File Listing。
(3)?在瀏覽數(shù)據(jù)方式中選擇Faceted Browse，單擊LINK進(jìn)入。這種方式能更方便地選取需要的數(shù)據(jù)。
(4)?選擇需要的時(shí)間段和物理量，單擊CONTINUE進(jìn)入下一步。
(5)?進(jìn)一步選取時(shí)間段、物理量（上一步已選擇，可跳過(guò)）、氣壓層和網(wǎng)格等參數(shù)，單擊UPDATE THE LIST以更新數(shù)據(jù)列表。
(6)?將頁(yè)面下拉，進(jìn)入下載選項(xiàng)。如圖：第一，選擇Unix下的Python腳本；第二，在RANGE SELECTION中選擇ON；第三，勾選列表中第一項(xiàng)和最后一項(xiàng)，那么所有數(shù)據(jù)都能被選上；第四，單擊CREATE創(chuàng)建腳本。
(7)?將腳本copy到文本中，用Linux環(huán)境下的Python運(yùn)行。如果列表有多頁(yè)，可以將對(duì)應(yīng)內(nèi)容整合到一個(gè)腳本中并運(yùn)行。
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