一、ERA-Interim
1. R，預(yù)報(bào)場(chǎng)，選的0點(diǎn)，step 12，2010年數(shù)據(jù)，0.5x0.5
2. R，預(yù)報(bào)場(chǎng)，step 12，選的剩下的12點(diǎn)，2010年數(shù)據(jù)
與上面對(duì)比。
哇地一聲在自習(xí)室忍住了哭，這兩個(gè)咋對(duì)比??？就是差了12個(gè)小時(shí)的預(yù)報(bào)值呀。
問(wèn)題來(lái)了：預(yù)報(bào)值和實(shí)測(cè)值到底差多少？差了半天的預(yù)測(cè)值又要如何修正？某一天某一點(diǎn)的預(yù)報(bào)值能代表一個(gè)月的數(shù)值嗎？公開(kāi)的數(shù)據(jù)中心里到底有沒(méi)有實(shí)測(cè)值來(lái)修正一下預(yù)報(bào)值？是不是徑流這種數(shù)據(jù)，難以用衛(wèi)星監(jiān)測(cè)到，沒(méi)有合適的模型計(jì)算全球范圍的數(shù)據(jù)，so，只有預(yù)測(cè)值？
預(yù)測(cè)值劃去，數(shù)據(jù)同化之后的數(shù)據(jù)產(chǎn)品，是模擬資料，可以用來(lái)分析、預(yù)測(cè)。
數(shù)據(jù)同化基本思想是不同源的實(shí)測(cè)資料、不同模型的模擬資料、不同的觀測(cè)項(xiàng)目，通過(guò)一定的技術(shù)手段把這些數(shù)據(jù)綜合在一起，實(shí)現(xiàn)序列拓展、精度提升或者是其他目的。
模擬資料，不一定是預(yù)測(cè)的；對(duì)無(wú)觀測(cè)資料地區(qū)或者未來(lái)時(shí)段，叫預(yù)測(cè)
二、ERA-Interim/Land
surface runoff，好像是日數(shù)據(jù)，好大的數(shù)據(jù)啊…不知道又要下多久。。。
先去吃飯吧。。
-----------更新至2017/07/08-----------
2017.8.14 更新
1. 再下過(guò)一個(gè)runoff，大家一起來(lái)找茬。。
Monthly means of daily forecast accumulations ,step 0-12
apps.ecmwf.int/datasets/data/interim-mdfa/levtype=sfc/requests/netcdf/59911de7dd5e9faa93b74684/
英文好重要T^T
2. 在氣象家園上看到這么個(gè)說(shuō)法，
bbs.06climate.com/forum.php
【Synoptic Monthly Means和Monthly Means of Daily Means ，做研究一般是下后者吧，前者好像是用于業(yè)務(wù)的~
? ?在ERA-40的Synoptic Monthly Means資料下有time select這個(gè)選項(xiàng)，這個(gè)選項(xiàng)下分成了四個(gè)時(shí)刻，假如我單選0:00這個(gè)時(shí)刻，那么得到的數(shù)據(jù)是每個(gè)月在0:00時(shí)刻的月平均值，單選12:00即每月該時(shí)刻的平均值。如果同時(shí)選0:00和12:00兩個(gè)時(shí)刻，那么得到的數(shù)據(jù)就是這兩個(gè)時(shí)刻所對(duì)應(yīng)的月平均值之和的一半，以此類推?！?br>
為此，同時(shí)選擇了step 0-12 與12-24的下載……
更正，氣象家園里的說(shuō)法是time select，并不是step。
2017.8.14 更新
向李老師尋求幫助后，
time select 并不會(huì)過(guò)多影響數(shù)據(jù)，具體應(yīng)該是預(yù)報(bào)的時(shí)間點(diǎn)。
step 的選項(xiàng)應(yīng)該是用來(lái)數(shù)據(jù)合成的時(shí)長(zhǎng)，越長(zhǎng)一般越有代表性。
Monthly Means of Daily Forecast Accumulations(mdfa) are similar toMonthly Means of Daily Meansbut for accumulated fields (eg precipitation, radiation). For example for precipitation, the data gives the monthly mean of daily (24 hour) precipitation. In addition, the data is available for three forecast steps, 0-12, 12-24 and 24-36 hours. Note these are not synoptic periods (00:00 to 12:00, etc), but specifies the provenance of the accumulated data, e.g. from the 0-to-12 hour forecast, 12-to-24 hour forecast, etc. In any case the data gives the monthly mean of daily 24 hour accumulation. Most users will want to use step 0-12.
1. ERA-Interim，
monthly means of forecast accumulated，下載徑流與蒸發(fā)數(shù)據(jù)，79年1月—16年12月，0.125°x0.125°。
unit：m ，月均值，需乘以當(dāng)月天數(shù)。
問(wèn)題：需處理單位，需乘以當(dāng)月天數(shù)得月總量。
runoff：?apps.ecmwf.int/datasets/data/interim-mdfa/levtype=sfc/selectors/netcdf/1000302/
2. 來(lái)個(gè)日數(shù)據(jù)試試水。
ERA-Interim，Daily，
Runoff， time：12:00 ， step = 12， 2016年1月數(shù)據(jù)，0.125°，
apps.ecmwf.int/datasets/data/interim-full-daily/levtype=sfc/selectors/netcdf/999398/
3.ERA-Interim，Monthly means of daily means
2m temperature 與 skin temperature 的比較
Skin temperature is defined as the temperature of the surface at radiative equilibrium. It forms the interface between soil, snow or ice and the atmosphere. Skin temperature in ERA-Interim (code 235) is derived from the surface energy balance. Over ocean, the skin temperature is set to the surface temperature.
You should use 2 meter temperature to compare with station observations, since "surface" air temperature observations are taken at 2 m above ground. Skin temperature in the model is the ground surface temperature (or SST over water) which can be quite different from the 2-m air temperature. Over land, skin temperature is calculated from the surface energy balance.
pass skin temperature
Monthly Means of Daily Means(moda) is available only for analysis and instantaneous forecast data. It is calculated like this, for example for temperature: You take the temperature readings for every day at 00:00, 06:00, 12:00, and 18:00 UTC for a month, and you average them. The result is a single mean temperature value (at each location) for the month. Then you do the same for the next month, and so on.
t2m 和 NOAA 的比較一下。
4.ERA-Interim，Synoptic Monthly means?
有total precipitation，等會(huì)比較一下。
Synoptic Monthly Means(mnth) from analyses are the monthly averages produced for each of the four main synoptic hours (00, 06, 12, and 18 UTC). For example with temperature: you take the temperature every day at 00:00, and then you average them over every month. So you get the average temperature at 00:00 in January, in February, etc. Then you do the same for the 06:00 temperature, then for the 12:00 temperature, and then for the 18:00 temperature. The result is the "Synoptic Monthly Mean" at 00:00, at 06:00, at 12:00 and at 18:00 for every month. "Synoptic Monthly Means" from forecasts are similar, except that they are for particular forecast start times and forecast steps.
SMM的數(shù)據(jù) pass
