A homogeneity test applied to precipitation data

118

This is a study of the changes in annual and seasonal precipitation amounts and variability, during the period 1951-2000, using MOPREDA MES . This dataset includes 1113 complete and homogeneous monthly precipitation time series from the Mediterranean Iberian Peninsula (IP), and corresponds to the five official Spanish hydrological divisions which drain into the Mediterranean Sea. The time series of annual and seasonal precipitation were used to test for trends. The absolute value of the anomaly time series was also tested for trends to identify changes in interannual variability of precipitation. The significance of these changes was assessed using the non-parametric Spearman rank test. The intensities of observed changes, both on mean values and variability, were estimated by using linear regression techniques. Finally, we analysed the area affected by different trends by using raster maps and spatial statistics, in addition to calculating the global balances for the five hydrological divisions. We detected high variability in precipitation regimes and conditions in the study area; nevertheless, a decrease in seasonal and annual precipitation has predominated in the east of the IP during the second half of the 20th century. On an annual scale, precipitation has diminished over 90.1% of the study area. Additionally, a high percentage of the territory was affected by diminishing precipitation at a seasonal level: 85% (of territory) in summer, 82% in spring, 64% during winter and 61% in autumn. Taking the study area as a whole, seasonal precipitation decreases are ranked as follows: summer (−22.5%), spring (−19.3%), winter (−7.3%), and autumn (−5.2%), with a decrease in the value of the global mean annual precipitation −12.4%. We also detected an increase of precipitation variability in winter (+23.5%) and summer (+11.4%), and a decrease in autumn and spring (−14.9 and −16.8%, respectively) with a global mean value of +7.8%.

Section: Precipitation Databasementioning

confidence: 99%

Seasonal precipitation trends in the Mediterranean Iberian Peninsula in second half of 20th century

Luis¹,

Gonzalez‐Hidalgo²,

Longares³

et al. 2008

118

“…To check the homogeneity of all recovered series, the Standard Normal Homogeneity Test (SNHT; Alexandersson, 1986), the Buishand Range test (Buishand, 1982), and the Pettitt test (Sneyers, 1995) were run over the entire series (JMA and their nineteenth-century extensions) of annual, seasonal, and monthly pressures and temperatures. For the motivation of the choice of these three location-specific homogeneity tests, see Wijngaard et al (2003).…”

Section: Data Homogenizationmentioning

confidence: 99%

Recovery of nineteenth‐century Tokyo/Osaka meteorological data in Japan

Zaiki

Können

Tsukahara

et al. 2006

We have recovered instrumental temperature and pressure observations from Tokyo covering the periods 1825-1828, 1839-1855, and 1872-1875; from Yokohama covering the periods 1860-1871 and 1874; from Osaka covering the periods 1828-1833 and 1869-1871; and from Kobe covering the periods 1869-1871 and 1875-1888. The newly recovered records contain data before the 1870s, which is a period where, until recently, no instrumental data in Japan were believed to exist. Their addition to the previous backward extension of Japanese series, as based on the recently recovered intermittent Dejima/Nagasaki series 1819-1878, implies that the nineteenth-century extension of the Japanese instrumental record no longer contains major temporal gaps. The recovered data were used for a preliminary calculation of the west-Japan temperature (WJT) series, which is a representative temperature series for the area. The existence of a warm epoch in the 1850s over W-Japan and a downward temperature trend till the early twentieth century, as previously inferred from documentary data, is confirmed from the WJT data. The pressure data implies that the temperature differences between the nineteenth and twentieth centuries are at least partly caused by a change in atmospheric circulation.

“…These data series are complete without missing values. The station data were checked for homogeneity with the aid of the Alexandersson (1986) homogeneity test, on a monthly basis and for each station separately. The results of the test verified that the data of all of the stations are homogeneous.…”

Section: Data Setsmentioning

confidence: 99%

Simulation of seasonal precipitation and raindays over Greece: a statistical downscaling technique based on artificial neural networks (ANNs)

Τολίκα

Maheras

Vafiadis

et al. 2006

Abstract:A statistical downscaling technique based on artificial neural network (ANN) was employed for the estimation of local changes on seasonal (winter, spring) precipitation and raindays for selected stations over Greece. Empirical transfer functions were derived between large-scale predictors from the NCEP/NCAR reanalysis and local rainfall parameters. Two sets of predictors were used: (1) the circulation-based 500 hPa and (2) its combination along with surface specific humidity and raw precipitation data (nonconventional predictor). The simulated time series were evaluated against observational data and the downscaling model was found efficient in generating winter and spring precipitation and raindays. The temporal evolution of the estimated variables was well captured, for both seasons. Generally, the use of the nonconventional predictors are attributed to the improvement of the simulated results. Subsequently, the present day and future changes on precipitation conditions were examined using large-scale data from the atmospheric general circulation model HadAM3P to the statistical model. The downscaled climate change signal for both precipitation and raindays, partly for winter and especially for spring, is similar to the signal from the HadAM3P direct output: a decrease of the parameters is predicted over the study area. However, the amplitude of the changes was different.