**500hPa height for Northern Hemisphere: 1873-1957**. (In anomaly, with
respect to 1961-90).

Surface climatic
variations are strongly related to the atmospheric circulation at lower to
middle troposphere (say, 500hPa). Thus it is possible to derive the 500hPa
heights from surface pressures and temperatures. This data set is reconstructed
using a forward stepwise regression approach. The linear relationship between
500hPa height (NCEP re-analysis data) and MSLP and temperatures are determined
on the basis of modern period with reliable observations (since late 1950s).
Both surface temperature and MSLP used here are obtained from Climatic Research
Unit of East Anglia University, U.K. (http://www.cru.uea.ac.uk/). Then, the
derived regression model is employed to compute the values for the period of
1873-1957. The relations are determined variably, i.e., depending on the
availability of surface data for each year each grid. See references for more
details.

**Availability:**

Reconstructed 500hPa
height anomalies are freely available here for each month:

January, February, March, April, May, June, July, August, September, October, November, and December. Zipped, each data file less than 1M in size. Unzipped about 2.1M.

**Data Format:**

For each month the
data are achieved in the order of years from 1873 to 1957 as:

1873 YYYY

1 Long Lat X1 X2
X3 X4 X5

…

649 Long Lat X1 X2
X3 X4 X5

1874 YYYY

1 Long Lat X1 X2 X3
X4 X5

…

649 Long Lat X1 X2
X3 X4 X5

…

Here YYYY is a
number related to the original data sets of MSLP and temperature;

Long and Lat are
longitude and latitude respectively;

X1 is the number
of variables used to calculate the 500hPa height at grid of Long and Lat;

X2 is the
calculated 500hPa height anomaly, in gpm;

X3, X4 and X5 are
statistic variables related to the regression model, i.e., the correlation,
confidence level and errors.

Spatial resolution
is the same as used in China Meteorological Administration in the routine
operation, roughly 10 by 5 degrees. There are 649 grids totally over the
northern hemisphere.

**References:**

龚道溢, 王绍武. 恢复近百年北半球500hPa高度场的试验. 热带气象学报，2000,16(2):148-154. (PDF)

Some discussions and applications of this data set can be found in:

慕巧珍, 王绍武, 蔡静宁, 谢志辉, 朱锦红. 近百年西太平洋副热带高压变化的模拟研究. 科学通报, 2002, 47(7),
550-553. (PDF)

慕巧珍, 王绍武, 朱锦红, 龚道溢. 近百年夏季西太平洋副热带高压的变化. 大气科学, 2001，25（6），787-797. (PDF)

Mu Qiaozhen, Wang Shaowu,
Zhu Jinhong, Gong Daoyi. Summer variations of the Western Pacific Subtropical
High during the last hundred years. *Chinese Journal of Atmospheric Sciences*,
2001, 25(4), 325-336. (PDF)

慕巧珍, 王绍武, 龚道溢. 近百年四季西太平洋副热带高压的变化. 气象学报, 2002, 60(6),668-679. (PDF)