Long-Term Trends of Sunshine Durations in Relation with Cloudiness and Relative Humidity in GAP Area, Turkey

Year 2017, Volume: 12 Issue: 2, 147 - 153, 30.06.2017

Tahsin Tonkaz Sevda Ocak

Abstract

Long-term trends of
monthly mean sunshine durations were analyzed utilizing non parametric tests
for Southeastern Anatolian Project (GAP) region. Correlation coefficients
between sunshine durations and relative humidity and cloudiness variable were
determined over the years. Climatic data between 1970 and 2005 from nine
meteorological stations scattered in the region were collected and used. The
non-parametric test results revealed that an upward trend was dominant
especially in the summer and early autumn months. Mann-Kendall test indicated
that the strongest trend was in August at Gaziantep station with Z value of
-6.63. Therefore, declining significant trends never observed in the months of
January, February, March, November, and December. Although, the highest upward
trend was observed in April at Mardin station, there was no significant rising
trend in the whole region for the same month. Cloudiness and relative humidity
data was satisfactorily explained the variation in sunshine durations. A common
significant negative correlation was found using non parametric test between
sunshine duration and relative humidity and cloudiness series. There were also
a few positive correlations, but none of them was significant. Additionally,
basic linear regression equation was employed in order to determine changes in
sunshine duration that Gaziantep station showed the highest decrease in July
with a value of 0.13 hours per year. Downward trends of sunshine duration could
be attributed to air quality changes which could affect adversely the
hydrological cycle and agricultural production. The overall findings support the
view that there is a climate change regionally or globally.

Keywords

Sunshine durations, non-parametric trend tests, Spearman Rho correlation test, GAP area

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