Articles | Volume 3, issue 3
https://doi.org/10.5194/wcd-3-1003-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/wcd-3-1003-2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Dynamics of gap winds in the Great Rift Valley, Ethiopia: emphasis on strong winds at Lake Abaya
Cornelius Immanuel Weiß
CORRESPONDING AUTHOR
Department of Atmospheric and Cryospheric Sciences (ACINN), University of Innsbruck, Innrain 52f, 6020 Innsbruck, Austria
Alexander Gohm
Department of Atmospheric and Cryospheric Sciences (ACINN), University of Innsbruck, Innrain 52f, 6020 Innsbruck, Austria
Mathias Walter Rotach
Department of Atmospheric and Cryospheric Sciences (ACINN), University of Innsbruck, Innrain 52f, 6020 Innsbruck, Austria
Thomas Torora Minda
Faculty of Meteorology and Hydrology, Arba Minch Water Technology Institute, Arba Minch University, P.O. Box 2221, Arba Minch, Ethiopia
Related authors
No articles found.
Johannes Mikkola, Victoria A. Sinclair, Giancarlo Ciarelli, Alexander Gohm, and Federico Bianchi
EGUsphere, https://doi.org/10.5194/egusphere-2025-6273, https://doi.org/10.5194/egusphere-2025-6273, 2026
This preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).
Short summary
Short summary
This study investigates the effect of black carbon on the diurnal winds within idealised mountain valleys using numerical simulations. Absorption of solar radiation by black carbon weakens the up-slope winds, but unexpectedly strengthens the afternoon up-valley winds. This happens because weaker up-slope winds remove less momentum from the valley, allowing the up-valley winds to become stronger even though the overall driving force is reduced by the absorption.
Johannes Mikkola, Alexander Gohm, Victoria A. Sinclair, and Federico Bianchi
Atmos. Chem. Phys., 25, 511–533, https://doi.org/10.5194/acp-25-511-2025, https://doi.org/10.5194/acp-25-511-2025, 2025
Short summary
Short summary
This study investigates the influence of valley floor inclination on diurnal winds and passive tracer transport within idealised mountain valleys using numerical simulations. The valley inclination strengthens the daytime up-valley winds but only up to a certain point. Beyond that critical angle, the winds weaken again. The inclined valleys transport the tracers higher up in the free troposphere, which would, for example, lead to higher potential for long-range transport.
Nevio Babić, Bianca Adler, Alexander Gohm, Manuela Lehner, and Norbert Kalthoff
Weather Clim. Dynam., 5, 609–631, https://doi.org/10.5194/wcd-5-609-2024, https://doi.org/10.5194/wcd-5-609-2024, 2024
Short summary
Short summary
Day-to-day weather over mountains remains a significant challenge in the domain of weather forecast. Using a combination of measurements from several instrument platforms, including Doppler lidars, aircraft, and radiosondes, we developed a method that relies primarily on turbulence characteristics of the lowest layers of the atmosphere. As a result, we identified new ways in which atmosphere behaves over mountains during daytime, which may serve to further improve forecasting capabilities.
Matthias Göbel, Stefano Serafin, and Mathias W. Rotach
Weather Clim. Dynam., 4, 725–745, https://doi.org/10.5194/wcd-4-725-2023, https://doi.org/10.5194/wcd-4-725-2023, 2023
Short summary
Short summary
On summer days over mountains, upslope winds transport moist air towards mountain tops and beyond, making local rain showers more likely. We use idealized simulations to investigate how mountain steepness affects this mechanism. We find that steeper mountains lead to a delayed onset and lower intensity of the storms, because less moisture accumulates over the ridges and the thermal updraft zone at the top is narrower and thus more prone to the intrusion of dry air from the environment.
Hetal P. Dabhi, Mathias W. Rotach, and Michael Oberguggenberger
Hydrol. Earth Syst. Sci., 27, 2123–2147, https://doi.org/10.5194/hess-27-2123-2023, https://doi.org/10.5194/hess-27-2123-2023, 2023
Short summary
Short summary
Spatiotemporally consistent high-resolution precipitation data on climate are needed for climate change impact assessments, but obtaining these data is challenging for areas with complex topography. We present a model that generates synthetic gridded daily precipitation data at a 1 km spatial resolution using observed meteorological station data as input, thereby providing data where historical observations are unavailable. We evaluate this model for a mountainous region in the European Alps.
Helen Claire Ward, Mathias Walter Rotach, Alexander Gohm, Martin Graus, Thomas Karl, Maren Haid, Lukas Umek, and Thomas Muschinski
Atmos. Chem. Phys., 22, 6559–6593, https://doi.org/10.5194/acp-22-6559-2022, https://doi.org/10.5194/acp-22-6559-2022, 2022
Short summary
Short summary
This study examines how cities and their surroundings influence turbulent exchange processes responsible for weather and climate. Analysis of a 4-year observational dataset for the Alpine city of Innsbruck reveals several similarities with other (flat) city centre sites. However, the mountain setting leads to characteristic daily and seasonal flow patterns (valley winds) and downslope windstorms that have a marked effect on temperature, wind speed, turbulence and pollutant concentration.
Manuel Saigger and Alexander Gohm
Weather Clim. Dynam., 3, 279–303, https://doi.org/10.5194/wcd-3-279-2022, https://doi.org/10.5194/wcd-3-279-2022, 2022
Short summary
Short summary
In this work a special form of a foehn wind in an Alpine valley with a large-scale northwesterly flow is investigated. The study clarifies the origin of the air mass and the mechanisms by which this air enters the valley. A trajectory analysis shows that the location where the main airstream passes the crest line is more suitable for a foehn classification than the local or large-scale wind direction. Mountain waves and a lee rotor were crucial for importing air into the valley.
Matthias Göbel, Stefano Serafin, and Mathias W. Rotach
Geosci. Model Dev., 15, 669–681, https://doi.org/10.5194/gmd-15-669-2022, https://doi.org/10.5194/gmd-15-669-2022, 2022
Short summary
Short summary
We present WRFlux, an open-source software that allows numerically consistent, time-averaged budget evaluation of prognostic variables for the numerical weather prediction model WRF as well as the transformation of the budget equations from the terrain-following grid of the model to the Cartesian coordinate system. We demonstrate the performance and a possible application of WRFlux and illustrate the detrimental effects of approximations that are inconsistent with the model numerics.
Johannes Horak, Marlis Hofer, Ethan Gutmann, Alexander Gohm, and Mathias W. Rotach
Geosci. Model Dev., 14, 1657–1680, https://doi.org/10.5194/gmd-14-1657-2021, https://doi.org/10.5194/gmd-14-1657-2021, 2021
Short summary
Short summary
This process-based evaluation of the atmospheric model ICAR is conducted to derive recommendations to increase the likelihood of its results being correct for the right reasons. We conclude that a different diagnosis of the atmospheric background state is necessary, as well as a model top at an elevation of at least 10 km. Alternative boundary conditions at the top were not found to be effective in reducing this model top elevation. The results have wide implications for future ICAR studies.
Cited articles
Bond, N. A., Dierking, C. F., and Doyle, J. D.: Research aircraft and wind
profiler observations in Gastineau Channel during a Taku wind event, Weather
Forecast., 21, 489–501, https://doi.org/10.1175/WAF932.1, 2006. a
Cao, G., Giambelluca, T. W., Stevens, D. E., and Schroeder, T. A.: Inversion
variability in the Hawaiian trade wind regime, J. Climate, 20,
1145–1160, https://doi.org/10.1175/JCLI4033.1, 2007. a
Carrillo, J., Guerra, J. C., Cuevas, E., and Barrancos, J.: Characterization of
the Marine Boundary Layer and the Trade-Wind Inversion over the Sub-tropical
North Atlantic, Bound.-Lay. Meteorol., 158, 311–330,
https://doi.org/10.1007/s10546-015-0081-1, 2016. a
Copernicus Climate Change Service (C3S) at ECMWF: ERA5 hourly data on pressure levels from 1959 to present, Copernicus Climate Change Service [data set], https://doi.org/10.24381/cds.bd0915c6, 2018. a
Copernicus Climate Change Service (C3S) at ECMWF:
ERA5-Land hourly data from 1950 to present, Copernicus Climate Change Service [data set],
https://doi.org/10.24381/cds.e2161bac, 2019. a
De Wekker, S. F. J. and Kossmann, M.: Convective Boundary Layer Heights Over
Mountainous Terrain – A Review of Concepts, Front. Earth Sci., 3, 77,
https://doi.org/10.3389/feart.2015.00077, 2015. a
Diro, G. T., Black, E., and Grimes, D. I. F.: Seasonal forecasting of Ethiopian
spring rains, Meteorol. Appl., 15, 73–83, https://doi.org/10.1002/met.63,
2007. a
Doran, J. C. and Zhong, S.: Thermally driven gap winds into the Mexico City
basin, J. Appl. Meteorol., 39, 1330–1340,
https://doi.org/10.1175/1520-0450(2000)039<1330:TDGWIT>2.0.CO;2, 2000. a, b, c
Drechsel, S. and Mayr, G. J.: Objective forecasting of Foehn winds for a
subgrid-scale alpine valley, Weather Forecast., 23, 205–218,
https://doi.org/10.1175/2007WAF2006021.1, 2008. a, b
Durran, D.: MOUNTAIN METEOROLOGY | Downslope Winds, in: Encyclopedia of
Atmospheric Sciences (Second Edition), edited by: North, G. R., Pyle, J., and
Zhang, F., pp. 69–74, Academic Press, Oxford, second edition edn.,
https://doi.org/10.1016/B978-0-12-382225-3.00288-7, 2015. a
Gebremariam, B.: Basin Scale Sedimentary and Water Quality: Responses to
External Forcing in Lake Abaya, Southern Ethiopian Rift Valley, Ph.D. thesis,
Freie Universität Berlin, https://doi.org/10.17169/refubium-11182, 2009. a, b, c, d
Gleixner, S., Keenlyside, N., Viste, E., and Korecha, D.: The El Niño effect
on Ethiopian summer rainfall, Clim. Dynam., 49, 1865–1883,
https://doi.org/10.1007/s00382-016-3421-z, 2017. a
Gohm, A. and Mayr, G. J.: Hydraulic aspects of föhn winds in an Alpine valley,
Q. J. Roy. Meteorol. Soc., 130, 449–480,
https://doi.org/10.1256/qj.03.28, 2004. a
Gohm, A., Mayr, G., Fix, A., and Giez, A.: On the onset of bora and the
formation of rotors and jumps near a mountain gap, Q. J. Roy. Meteorol. Soc., 134, 21–46, https://doi.org/10.1002/qj.206, 2008. a
Gohm, A., Mayr, G. J., Darby, L. S., and Banta, R. M.: Evolution and structure
of a cold front in an Alpine valley as revealed by a Doppler lidar, Q. J. Roy. Meteorol. Soc., 136, 962–977,
https://doi.org/10.1002/qj.609, 2010. a
Grisogono, B. and Belušić, D.: A review of recent advances in understanding
the meso- and microscale properties of the severe Bora wind, Tellus A, 61, 1–16,
https://doi.org/10.1111/j.1600-0870.2008.00369.x, 2009. a
Haid, M., Gohm, A., Umek, L., Ward, H. C., Muschinski, T., Lehner, L., and
Rotach, M. W.: Foehn–cold pool interactions in the Inn Valley during PIANO
IOP2, Q. J. Roy. Meteorol. Soc., 146, 1232–1263,
https://doi.org/10.1002/qj.3735, 2020. a
Haile, A. T., Rientjes, T., Gieske, A., and Gebremichael, M.: Rainfall
variability over mountainous and adjacent lake areas: The case of Lake Tana
basin at the source of the Blue Nile River, J. Appl. Meteorol.
Climatol., 48, 1696–1717, https://doi.org/10.1175/2009JAMC2092.1, 2009. a
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers,
D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo,
G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De
Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R.,
Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L.,
Healy, S., Hogan, R, J., Hólm, E., Janisková, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum,
I., Vamborg, F., Villaume, S., and Thépaut, J.-N.: The ERA5 global reanalysis, Q. J. Roy. Meteorol. Soc., 146, 999–2049, https://doi.org/10.1002/qj.3803, 2020. a, b
Hong, S. and Lim, J.: The WRF Single-Moment 6-Class Microphysics Scheme (WSM6),
Journal of the Korean Meteorological Society, 42, 129–151, 2006. a
Iacono, M. J., Delamere, J. S., Mlawer, E. J., Shephard, M. W., Clough, S. A.,
and Collins, W. D.: Radiative forcing by long-lived greenhouse gases:
Calculations with the AER radiative transfer models, J. Geophys.
Res.-Atmos., 113, 2–9, https://doi.org/10.1029/2008JD009944, 2008. a
Janjic, Z.: Nonsingular Implementation of the Mellor-Yamada Level 2.5 Scheme in
the NCEP Meso model, NCEP Office Note, 437, 61,
https://repository.library.noaa.gov/view/noaa/11409 (last
access: 23 March 2022), 2002. a
Klemp, J. B., Dudhia, J., and Hassiotis, A. D.: An upper gravity-wave absorbing
layer for NWP applications, Mon. Weather Rev., 136, 3987–4004,
https://doi.org/10.1175/2008MWR2596.1, 2008. a
Korecha, D. and Sorteberg, A.: Validation of operational seasonal rainfall
forecast in Ethiopia, Water Resour. Res., 49, 7681–7697,
https://doi.org/10.1002/2013WR013760, 2013. a
Kossmann, M. and Sturman, A. P.: Pressure-driven channeling effects in bent
valleys, J. Appl. Meteorol., 42, 151–158,
https://doi.org/10.1175/1520-0450(2003)042<0151:PDCEIB>2.0.CO;2, 2003. a, b, c
Lemmens, P., Teffera, F. E., Wynants, M., Govaert, L., Deckers, J., Bauer, H.,
Woldeyes, F., Brendonck, L., Bouillon, S., and Meester, L. D.: Intra- and
interspecific niche variation as reconstructed from stable isotopes in two
ecologically different Ethiopian Rift Valley lakes, Funct. Ecol., 31,
1482–1492, https://doi.org/10.1111/1365-2435.12852, 2017. a, b
Mengistu, B. B., Unbushe, D., and Abebe, E.: Invasion of Water Hyacinth
(Eichhornia crassipes) Is Associated with Decline in Macrophyte Biodiversity
in an Ethiopian Rift-Valley Lake-Abaya, Open J. Ecol., 07,
667–681, https://doi.org/10.4236/oje.2017.713046, 2017. a
Minda, T. T.: Weather and crop dynamics in a complex terrain, the Gamo
Highlands – Ethiopia: Towards a high-resolution and model-observation based
approach, Ph.D. thesis, Wageningen University, https://doi.org/10.18174/497431 (last
access: 23 March 2022), 2019. a, b
Minda, T. T., van der Molen, M. K., Heusinkveld, B. G., Struik, P. C., and
de Arellano, J. V. G.: Observational characterization of the synoptic and
mesoscale circulations in relation to crop dynamics: Belg 2017 in the Gamo
Highlands, Ethiopia, Atmosphere, 9, 398, https://doi.org/10.3390/atmos9100398,
2018a. a, b, c
Minda, T. T., van der Molen, M. K., Struik, P. C., Combe, M., Jiménez, P. A.,
Khan, M. S., and de Arellano, J. V. G.: The combined effect of elevation and
meteorology on potato crop dynamics: A 10-year study in the Gamo Highlands,
Ethiopia, Agr. Forest Meteorol., 262, 166–177,
https://doi.org/10.1016/j.agrformet.2018.07.009, 2018b. a
Munday, C., Engelstaedter, S., Ouma, G., Ogutu, G., Olago, D., Ong’ech, D.,
Lees, T., Wanguba, B., Nkatha, R., Ogalo, C., Gàlgalo, R. A., Dokata, A. J.,
Kirui, E., Hope, R., and Washington, R.: Observations of the Turkana Jet and
the East African dry tropics: the RIFTJet field campaign, B.
Am. Meteorol. Soc., 103, E1828–E1842, https://doi.org/10.1175/BAMS-D-21-0214.1, 2022. a, b, c
Nakanishi, M. and Niino, H.: Development of an improved turbulence closure
model for the atmospheric boundary layer, J. Meteorol.
Soc. Japan, 87, 895–912, https://doi.org/10.2151/jmsj.87.895, 2009. a
Nicholson, S.: The Turkana low-level jet: Mean climatology and association with
regional aridity, Int. J. Climatol., 36, 2598–2614,
https://doi.org/10.1002/joc.4515, 2016. a, b
Pan, F. and Smith, R. B.: Gap Winds and Wakes: SAR Observations and Numerical
Simulations, J. Atmos. Sci., 56, 905–923,
https://doi.org/10.1175/1520-0469(1999)056<0905:GWAWSO>2.0.CO;2, 1999. a, b, c
Park, S. H., Klemp, J. B., and Kim, J. H.: Hybrid mass coordinate in WRF-ARW
and its impact on upper-level turbulence forecasting, Mon. Weather Rev.,
147, 971–985, https://doi.org/10.1175/MWR-D-18-0334.1, 2019. a
Rife, D. L., Pinto, J. O., Monaghan, A. J., Davis, C. A., and Hannan, J. R.:
Global Distribution and Characteristics of Diurnally Varying Low-Level Jets,
J. Climate, 23, 5041–5064, https://doi.org/10.1175/2010JCLI3514.1, 2010. a
Scheffer, M.: Ecology of Shallow Lakes, Springer Netherlands,
https://doi.org/10.1007/978-1-4020-3154-0, 2004. a
Sjoukje, P., Kew, S. F., van Oldenborgh, G. J., Otto, F., O'Keefe, S.,
Haustein, K., King, A., Zegeye, A., Eshetu, Z., Hailemariam, K., Singh, R.,
Jjemba, E., Funk, C., and Cullen, H.: Attribution analysis of the Ethiopian
drought of 2015, J. Climate, 31, 2465–2486,
https://doi.org/10.1175/JCLI-D-17-0274.1, 2018. a
Skamarock, W., Klemp, J., Dudhia, J., Gill, D., Zhiquan, L., Berner, J., Wang,
W., Powers, J., Duda, M. G., Barker, D. M., and Huang, X.-Y.: A Description
of the Advanced Research WRF Model Version 4.1, NCAR Technical Note
NCAR/TN-556+STR, p. 145, https://doi.org/10.5065/1dfh-6p97, 2019. a, b
Teffera, F. E.: The ecology of the major Ethiopian Rift Valley lakes Abaya and
Chamo, with special reference to water quality and food web structure, Ph.D.
thesis, KU Leuven,
https://limo.libis.be/primo-explore/fulldisplay?docid=LIRIAS1706016&context=L&vid=Lirias
(last access: 23 March 2022), 2016. a
Teffera, F. E., Lemmens, P., Deriemaecker, A., Brendonck, L., Dondeyne, S.,
Deckers, J., Bauer, H., Gamo, F. W., and Meester, L. D.: A call to action:
strong long-term limnological changes in the two largest Ethiopian Rift
Valley lakes, Abaya and Chamo, Inland Waters, 7, 129–137,
https://doi.org/10.1080/20442041.2017.1301309, 2017. a, b
Tewari, M., Chen, F., Wang, W., Dudhia, J., LeMone, M. A., Mitchell, K., Ek,
M., Gayno, G., Wegiel, J., and Cuenca, R. H.: Implementation and verification
of the unified noah land surface model in the WRF model[presentation], in:
20th Conference on Weather Analysis and Forecasting/16th Conference on
Numerical Weather Prediction, pp. 11–15,
http://n2t.net/ark:/85065/d7fb523p (last access: 23 March 2022), 2004. a
University Corporation for Atmospheric Research:
The Weather Research and Forecasting Model, University Corporation for Atmospheric Research [code], https://github.com/wrf-model/WRF (last access: 17 August 2022), 2019. a
Vizy, E. K. and Cook, K. H.: Observed relationship between the Turkana
low-level jet and boreal summer convection, Clim. Dynam., 53, 4037–4058,
https://doi.org/10.1007/s00382-019-04769-2, 2019.
a
Yu, X. and Lee, T. Y.: Role of convective parameterization in simulations of a
convection band at grey-zone resolutions, Tellus A, 62, 617–632,
https://doi.org/10.1111/j.1600-0870.2010.00470.x, 2010. a
Zekarias, T., Govindu, V., Kebede, Y., and Gelaw, A.: Degradation of wetlands
and livelihood benefits of Lake Abaya-Chamo wetland, southern Ethiopia,
Current Research in Environmental Sustainability, 3, 100060,
https://doi.org/10.1016/j.crsust.2021.100060, 2021. a
Zinabu, G. M., Kebede-Westhead, E., and Desta, Z.: Long-term changes in
chemical features of waters of seven Ethiopian rift-valley lakes,
Hydrobiologia, 477, 81–91, https://doi.org/10.1023/A:1021061015788, 2002. a
Zängl, G.: Idealized numerical simulations of shallow föhn, Q. J. Roy. Meteorol. Soc., 128, 431–450,
https://doi.org/10.1256/003590002321042045, 2002. a
Zängl, G. and Gonzalez Chico, S.: The thermal circulation of a grand plateau:
Sensitivity to the height, width, and shape of the plateau, Mon. Weather
Rev., 134, 2581–2600, https://doi.org/10.1175/MWR3207.1, 2006. a, b
Short summary
Two gap flow events in the Great Rift Valley in Ethiopia were investigated based on observations, ERA5 reanalysis data, and simulations with the numerical weather prediction model WRF. The main focus was on strong winds in the area around Lake Abaya since the winds may generate waves on the lake which help to sustain the lake's ecology. That is important in terms of food supply for the local population. The gap winds exhibit a diurnal cycle and a seasonal dependence.
Two gap flow events in the Great Rift Valley in Ethiopia were investigated based on...