Preprints
https://doi.org/10.5194/hess-2021-250
https://doi.org/10.5194/hess-2021-250

  09 Jun 2021

09 Jun 2021

Review status: this preprint is currently under review for the journal HESS.

Performance of the Global Forecast System's Medium-Range Precipitation Forecasts in the Niger River Basin

Haowen Yue1, Mekonnen Gebremichael1, and Vahid Nourani2 Haowen Yue et al.
  • 1Department of Civil and Environmental Engineering, University of California, Los Angeles, CA 90095-1593
  • 2Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran

Abstract. Weather forecast information has the potential to improve water resources management, energy, and agriculture. This study evaluates the accuracy of medium-range (1–15 day) precipitation forecasts from the Global Forecast System (GFS) over watersheds of eight major dams in the Niger river basin. The Niger basin lies in three latitudinal/climatic sub-regions: Sahel (latitude > 12° N) with annual rainfall of rainfall 400–600 mm, Savannah (latitude 8°–12° N) with annual rainfall of 900–1200 mm, and Guinea Coast (latitude 4°–8° N) with annual rainfall of 1500–2000 mm. The GFS forecast tends to overestimate rainfall in the Guinea Coast and western parts of the Savannah, but estimates well in the Sahel. The overall performance of daily GFS forecast was found to be satisfactory for two watersheds, namely, Kainji (the largest watershed in the basin, predominantly located in the Sahel), and Markala (the second largest watershed, located partly in the Sahel and partly in the Savannah). However, the performance of daily GFS forecast was found to be unsatisfactory in the remaining six watersheds, with GFS forecasts characterized by large random errors, high false alarm, high overestimation bias of low rain rates, and large underestimation bias of heavy rain rates. The GFS forecast accuracy decreases with increasing lead time. The accuracy of GFS forecasts could be improved by applying post-processing techniques involving near-real time satellite rainfall products.

Haowen Yue et al.

Status: open (until 29 Sep 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-250', Anonymous Referee #1, 10 Jul 2021 reply
    • AC1: 'Reply on RC1', Haowen Yue, 19 Jul 2021 reply
  • CC1: 'Comment on hess-2021-250', Koray Kamil Yilmaz, 02 Sep 2021 reply

Haowen Yue et al.

Haowen Yue et al.

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Short summary
The development of high-resolution global precipitation forecasts and the lack of reliable precipitation forecasts over Africa motivates this work to evaluate the precipitation forecasts from the Global Forecast System over the Niger river basin in Africa. The GFS forecast, at a 15-day accumulation timescale, has acceptable performance, however, the forecasts are highly biased. It is recommended to apply bias correction of GFS forecasts before its applicaiton.