The Influence of Gravity Waves on the Climate Change Over Upper Blue Nile Basin in Ethiopia

Mapping Intimacies ◽

10.21203/rs.3.rs-64803/v1 ◽

2020 ◽

Author(s):

Megbar Birhan ◽

Balew Adane ◽

Tamiru Negussie

Keyword(s):

Climate Change ◽

Gravity Wave ◽

Gravity Waves ◽

Spatiotemporal Variability ◽

Nile Basin ◽

Blue Nile ◽

Blue Nile Basin ◽

Energy And Momentum ◽

Precipitation And Temperature ◽

Upper Blue Nile Basin

Abstract Precipitation and temperature are the most fundamental meteorological/weather parameters with high spatiotemporal variability over any region of the Globe. Over Ethiopia, Upper Blue Nile basin (UBNB) is the major water resources for irrigation and societal needs not only for Ethiopia but also for downstream countries. However, the exact mechanism to study climate change is not yet satisfactory. Climate variability over UBNB is too high due to its variable topographical features. Gravity wave is one of the most influencing factors to climate change. However, there is no study conducted by considering gravity wave activities on the effect of climate change over UBNB. Therefore, the attempt is made the influence of gravity waves on climate change and variability over UBNB. To this end, we inferred different data sources (reanalysis and ground based). Kinetic energy and momentum equations were used in this study. The results indicate that the reanalysis (ECMWF) precipitation and temperature data were well agreed to the ground based data with correlation coefficient of 0.83 and 0.41 respectively. Strong gravity wave takes tropospheric cloud to stratosphere which causes drought events, while weak gravity wave moves lower tropospheric cloud to tropopause which leads to the occurrence floods. Generally, gravity wave activities affected precipitation and temperature distribution during rainy season. Hence, future study is quite useful to investigate the frequency of high gravity wave occurrence in connection to Ethiopian drought events.

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Influence of downscaling methods in projecting climate change impact on hydrological extremes of upper Blue Nile basin

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-10-7857-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 7857-7896 ◽

Cited By ~ 7

Author(s):

M. T. Taye ◽

P. Willems

Keyword(s):

Climate Change ◽

Climate Model ◽

Weather Generator ◽

Nile Basin ◽

Blue Nile ◽

Downscaling Method ◽

Blue Nile Basin ◽

Good For ◽

The Impact ◽

Upper Blue Nile Basin

Abstract. Methods from two statistical downscaling categories were used to investigate the impact of climate change on high rainfall and flow extremes of the upper Blue Nile basin. The main downscaling differences considered were on the rainfall variable while a generally similar method was applied for temperature. The applied downscaling methods are a stochastic weather generator, LARS-WG, and an advanced change factor method, the Quantile Perturbation Method (QPM). These were applied on 10 GCM runs and two emission scenarios (A1B and B1). The downscaled rainfall and evapotranspiration were input into a calibrated and validated lumped conceptual model. The future simulations were conducted for 2050s and 2090s horizon and were compared with 1980–2000 control period. From the results all downscaling methods agree in projecting increase in temperature for both periods. Nevertheless, the change signal on the rainfall was dependent on the climate model and the downscaling method applied. LARS weather generator was good for monthly statistics although caution has to be taken when it is applied for impact analysis dealing with extremes, as it showed a deviation from the extreme value distribution's tail shape. Contrary, the QPM method was good for extreme cases but only for good quality daily climate model data. The study showed the choice of downscaling method is an important factor to be considered and results based on one downscaling method may not give the full picture. Regardless, the projections on the extreme high flows and the mean main rainy season flow mostly showed a decreasing change signal for both periods. This is either by decreasing rainfall or increasing evapotranspiration depending on the downscaling method.

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