Variations of Seasonal Precipitation in the Yellow River Basin and Its Relationship to General Circulation and SST

<p>Based on the precipitation data from 1961 to 2017 in the Yellow River Basin and NCEP/NCAR reanalysis data, the variation characteristics of seasonal precipitation in the Yellow River Basin and its relationship to the circulation patterns were analyzed. Furthermore, effect of sea surface temperature (SST) on the seasonal precipitation was discussed. The results were as follows: (1) The precipitation in spring, summer and autumn all presented non-significant decreasing trends, while that in winter presented a non-significant upward trend. (2) The inter-annual and inter-decadal fluctuations of the precipitation of each season were evident. The fluctuation in winter was the most obvious, followed by that in spring and autumn, with that in summer most stable. Moreover, the precipitation in summer, autumn and winter in 1990s was the least. (3) When the precipitation in spring, autumn and winter was significantly above (below) normal, the 500&thinsp;hPa height anomaly field over Eurasia mid-high latitude of the corresponding period presented “positive (negative) in east and negative (positive) in west”. While, when the precipitation in summer was significantly above (below) normal, the height anomaly field presented “<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>+</mo><mo>(</mo><mo>-</mo><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="871b7b9633d984ed536db43584a077d9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="piahs-383-5-2020-ie00001.svg" width="25pt" height="12pt" src="piahs-383-5-2020-ie00001.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mo>(</mo><mo>+</mo><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="3ff704e2c3a00477b8ed4c3a70f564f0"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="piahs-383-5-2020-ie00002.svg" width="25pt" height="12pt" src="piahs-383-5-2020-ie00002.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>+</mo><mo>(</mo><mo>-</mo><mo>)</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="12pt" class="svg-formula" dspmath="mathimg" md5hash="c5b8ad17be2977064942daf4979c62d9"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="piahs-383-5-2020-ie00003.svg" width="25pt" height="12pt" src="piahs-383-5-2020-ie00003.png"/></svg:svg></span></span>”, and the West Pacific subtropical high was stronger (weaker) and lying more northward (southward). Additionally, when the precipitation in each season was significantly above (below) normal, the 850&thinsp;hPa wind anomalies showed abnormal southerly (northerly) winds in Eastern China, which was favorable (unfavorable) to transport water vapor from the South China Sea and the Western North Pacific to the Yellow River Basin. (4) The spring precipitation was above (below) normal during the period of El Niño (La Niña), while the summer, autumn and winter precipitation presented the opposite characteristics.</p>