Correcting position error in rainfall estimates using temporal and spatial warping

2020 ◽  
Author(s):  
Camille Le Coz ◽  
Arnold Heemink ◽  
Martin Verlaan ◽  
Marie-claire ten Veldhuis ◽  
Nick van de Giesen
Keyword(s):  
Bias Correction ◽  
Monsoon Season ◽  
Position Error ◽  
Rainfall Event ◽  
Sub Saharan Africa ◽  
Registration Method ◽  
Rainfall Events ◽  
Meteorological Observatory ◽  
Sub Saharan ◽  
Rainfall Estimates

<p>An increasing number of satellite-based rainfall estimates, with ever finer resolution, are becoming available. They are particularly valuable in regions with sparse radar and gauge networks. For example, in most of sub-Saharan Africa, the gauge network is not dense enough to represent the high variability of the rainfall during the monsoon season. However, satellite-based estimates can be subject to errors in position and/or timing of the rainfall events, in addition to errors in the intensity.<br>Many satellite-based estimates use gauge measurements for bias correction. Bias correction methods focus on the intensity errors, and do not correct the position error explicitly. We propose to gauge-adjust the satellite-based estimates with respect to the position and time. We investigate two approaches: spatial and temporal warping. The first one is based on a spatial mapping and correct the spatial position while keeping the time constant. The second uses a temporal mapping and keeps the spatial domain unchanged. The mappings are derived through a fully automatic registration method. That is, only the gauge and satellite-based estimates are needed as inputs. There is no need to manually predefine the rain features.<br>The spatial and temporal approaches are both applied to a rainfall event during the monsoon season in southern Ghana. The Trans-African Hydro-Meteorological Observatory (TAHMO) gauge network is used to gauge-adjust the IMERG-Late (Integrated Multi-Satellite Retrievals for GPM) satellite-based estimates. The two approaches are evaluated with respect to the timing, the location and the intensity of the rainfall event.</p>

scholarly journals Correcting Position Error in Precipitation Data Using Image Morphing

2019 ◽  
Vol 11 (21) ◽  
pp. 2557 ◽  
Author(s):  
Camille Le Coz ◽  
Arnold Heemink ◽  
Martin Verlaan ◽  
Marie-claire ten Veldhuis ◽  
Nick van de Giesen
Keyword(s):  
Monsoon Season ◽  
Real Data ◽  
Sub Saharan Africa ◽  
Rain Event ◽  
Spatial Transformation ◽  
Image Morphing ◽  
Rainfall Events ◽  
Position Errors ◽  
First Case ◽  
Meteorological Observatory

Rainfall estimates based on satellite data are subject to errors in the position of the rainfall events in addition to errors in their intensity. This is especially true for localized rainfall events such as the convective rainstorms that occur during the monsoon season in sub-Saharan Africa. Many satellite-based estimates use gauge information for bias correction. However, bias adjustment methods do not correct the position errors explicitly. We propose to gauge-adjust satellite-based estimates with respect to the position using a morphing method. Image morphing transforms an image, in our case a rainfall field, into another one, by applying a spatial transformation. A benefit of this approach is that it can take both the position and the intensity of a rain event into account. Its potential is investigated with two case studies. In the first case, the rain events are synthetic, represented by elliptic shapes, while the second case uses real data from a rainfall event occurring during the monsoon season in southern Ghana. In the second case, the satellite-based estimate IMERG-Late (Integrated Multi-Satellite Retrievals for GPM ) is adjusted to gauge data from the Trans-African Hydro-Meteorological Observatory (TAHMO) network. The results show that the position errors can be corrected, while preserving the higher spatial variability of the satellite-based estimate.

scholarly journals Comparison of Rainfall Products over Sub-Saharan Africa

2020 ◽  
Vol 21 (4) ◽  
pp. 553-596 ◽  
Author(s):  
Camille Le Coz ◽  
Nick van de Giesen
Keyword(s):  
Sub Saharan Africa ◽  
Rainfall Regime ◽  
Socioeconomic Impacts ◽  
African Rainfall ◽  
Factors Influencing ◽  
Radar Networks ◽  
Sub Saharan ◽  
Rainfall Climatology ◽  
Different Parts ◽  
Rainfall Estimates

AbstractAn ever-increasing number of rainfall estimates is available. They are used in many important applications such as flood/drought monitoring, water management, or climate monitoring. Such data are especially valuable in sub-Saharan Africa, where rainfall has considerable socioeconomic impacts and the gauge and radar networks are sparse. The choice of a rainfall product can significantly influence the performance of such applications. This study reviews previous works, evaluating or comparing rainfall products over different parts of sub-Saharan Africa. Three types of rainfall products are considered: the gauge-only, the satellite-based, and the reanalysis ones. In addition to the global rainfall products, we included three regional ones specifically developed for Africa: the African Rainfall Climatology version 2 (ARC2), the Rainfall Estimate version 2 (RFE2), and the Tropical Applications of Meteorology Using Satellite Data and Ground-Based Observations (TAMSAT) African Rainfall Climatology and Time Series (TARCAT). The gauge density, the orography, and the rainfall regime, which vary with the climate and the season, influence the performance of the rainfall products. This review does not focus on comparing results, as many other publications doing so are already available. Instead, we propose this review as a guide through the different rainfall products available over Africa, and the factors influencing their performances. With this review, the reader can make informed decisions about which products serve their specific purpose best.

Water, Weather and Climate Services for Africa: the case of Ghana and Kenya

2020 ◽  
Author(s):  
Frank Ohene Annor ◽  
Nick van de Giesen ◽  
Marie-Claire ten Veldhuis
Keyword(s):  
Value Chain ◽  
Weather Forecast ◽  
Laser Speckle ◽  
Sub Saharan Africa ◽  
Climate Projections ◽  
Distributed Temperature Sensing ◽  
Climate Services ◽  
Meteorological Observatory ◽  
Weather And Climate ◽  
Sub Saharan

<p>Close to 80% of Sub-Saharan African farmers rely on rainfed agriculture.  This makes it important that the weather and climate in this region is well understood, since it accounts for more than 15% of the GDP for instance in Ghana and Kenya. However, uncertainties in weather forecast and climate projections are very high in particular for this region, which leads to poor weather and climate services for agriculture production. One of the underlying factors among many is the poor conditions of weather and climate infrastructure in Sub-Saharan Africa.  The Trans-African Hydro-Meteorological Observatory (TAHMO) together with some National Meteorological and Hydrological Services (NMHSs) in Africa and other partners through the TWIGA project (http://twiga-h2020.eu/) are building a network of weather and hydrological stations to address this need. This network builds on the over 500 TAHMO stations in countries of interest like Ghana, Kenya, Uganda, South Africa, and Mozambique.</p><p>The observation network includes automatic weather stations, soil moisture sensors, Global Navigation Satellite System (GNSS) receivers, distributed temperature sensing (DTS), lightning sensors, neutron counters, evaporometers, laser speckle scintillometers, accelerometers for tree weighing, intervalometer rain gauges, flood mapper using citizen science mobile applications (Apps) and crop doctor using drones and Apps. The project has accelerated the Technology Readiness Levels (TRLs) of these innovations with some already set up for operational purposes delivering the first set of TWIGA services such as “How humid is my environment?; Crop detection and condition monitoring; Weather-based alerts for citizens/farmers; Area-specific near real-time weather forecast for farmers; Crop insurance based on soil index; Plastic accumulation monitor; Short-term prediction for solar energy; and Precipitable water vapour monitoring with TWIGA GNSS stations. These new innovations and the services developed using the value chain approach is a game changer for Sub-Saharan Africa.</p>

scholarly journals Spatial and Time Warping for Gauge Adjustment of Rainfall Estimates

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1510
Author(s):  
Camille Le Le Coz ◽  
Arnold Heemink ◽  
Martin Verlaan ◽  
Nick van de van de Giesen
Keyword(s):  
Bias Correction ◽  
Positive Impact ◽  
Sub Saharan Africa ◽  
Rain Event ◽  
Time Warping ◽  
Deformation Method ◽  
Timing Errors ◽  
Position Errors ◽  
Southern Ghana ◽  
Rainfall Estimates

Many satellite-based estimates use gauge information for bias correction. In general, bias-correction methods are focused on the intensity error and do not explicitly correct possible position or timing errors. However, position and timing errors in rainfall estimates can also lead to errors in the rainfall occurrence or the intensity. This is especially true for localized rainfall events such as the convective rainstorms occurring during the rainy season in sub-Saharan Africa. We investigated the use of warping to correct such errors. The goal was to gauge-adjust satellite-based estimates with respect to the position and the timing of the rain event, instead of its intensity. Warping is a field-deformation method that transforms an image into another one. We compared two methods, spatial warping focusing on the position errors and time warping for the timing errors. They were evaluated on two case studies: a synthetic rainfall event represented by an ellipse and a rain event in southern Ghana during the monsoon season. In both cases, the two warping methods reduced significantly the respective targeted (position or timing) errors. In the southern Ghana case, the average position error was decreased by about 45 km by the spatial warping and the average timing error was decreased from more than 1 h to 0.2 h by the time warping. Both warping methods also improved the continuous statistics on the intensity: the correlation went from 0.18 to at least 0.62 after warping in the southern Ghana case. The spatial warping seems more interesting because of its positive impact on both position and timing errors.

scholarly journals Exploring the Potential of the Cost-Efficient TAHMO Observation Data for Hydro-Meteorological Applications in Sub-Saharan Africa

Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3308
Author(s):  
Julia Schunke ◽  
Patrick Laux ◽  
Jan Bliefernicht ◽  
Moussa Waongo ◽  
Windmanagda Sawadogo ◽  
...  
Keyword(s):  
Evaluation Studies ◽  
Climate Impact ◽  
Sub Saharan Africa ◽  
Observation Data ◽  
Climate Conditions ◽  
Meteorological Observatory ◽  
Spatial Dependencies ◽  
Sub Saharan ◽  
Cost Efficient ◽  
The Cost

The Trans-African Hydro-Meteorological Observatory (TAHMO) is a promising initiative aiming to install 20,000 stations in sub-Saharan Africa counteracting the decreasing trend of available measuring stations. To achieve this goal, it is particularly important that the installed weather stations are cost-efficient, appropriate for African conditions, and reliably measure the most important variables for hydro-meteorological applications. Since there exist no performance studies of TAHMO stations while operating in Africa, it is necessary to investigate their performance under different climate conditions. This study provides a first analysis of the performance of 10 selected TAHMO stations across Burkina Faso (BF). More specifically, the analysis consists of missing value statistics, plausibility tests of temperature (minimum, maximum) and precipitation, spatial dependencies (correlograms) by comparison with daily observations from synoptical stations of the BF meteorological service as well as cross-comparison between the TAHMO stations. Based on the results of this study for BF for the period from May 2017 to December 2020, it is concluded that TAHMO potentially offers a reliable and cost-efficient solution for applications in hydro-meteorology. The usage of wind speed measurements cannot be recommended without reservation, at least not without bias correcting of the data. The limited measurement period of TAHMO still prevents its usability in climate (impact) research. It is also stressed that TAHMO cannot replace existing observation networks operated by the local meteorological services, but it can be a complement and has great potential for detailed spatial analyses. Since restricted to BF in this analysis, more evaluation studies of TAHMO are needed considering different environmental and climate conditions across SSA.

RTS,S/AS01, a vaccine targeting pre-erythrocytic stages of Plasmodium falciparum

2017 ◽  
Vol 1 (6) ◽  
pp. 533-537
Author(s):  
Lorenz von Seidlein ◽  
Borimas Hanboonkunupakarn ◽  
Podjanee Jittmala ◽  
Sasithon Pukrittayakamee
Keyword(s):  
Protective Efficacy ◽  
Age Groups ◽  
Sub Saharan Africa ◽  
Phase Iii ◽  
European Medicines Agency ◽  
Older Children ◽  
Pivotal Phase ◽  
Malaria Epidemiology ◽  
Maximum Benefit ◽  
Sub Saharan

RTS,S/AS01 is the most advanced vaccine to prevent malaria. It is safe and moderately effective. A large pivotal phase III trial in over 15 000 young children in sub-Saharan Africa completed in 2014 showed that the vaccine could protect around one-third of children (aged 5–17 months) and one-fourth of infants (aged 6–12 weeks) from uncomplicated falciparum malaria. The European Medicines Agency approved licensing and programmatic roll-out of the RTSS vaccine in malaria endemic countries in sub-Saharan Africa. WHO is planning further studies in a large Malaria Vaccine Implementation Programme, in more than 400 000 young African children. With the changing malaria epidemiology in Africa resulting in older children at risk, alternative modes of employment are under evaluation, for example the use of RTS,S/AS01 in older children as part of seasonal malaria prophylaxis. Another strategy is combining mass drug administrations with mass vaccine campaigns for all age groups in regional malaria elimination campaigns. A phase II trial is ongoing to evaluate the safety and immunogenicity of the RTSS in combination with antimalarial drugs in Thailand. Such novel approaches aim to extract the maximum benefit from the well-documented, short-lasting protective efficacy of RTS,S/AS01.

Mortality and Society in Sub-Saharan Africa

1993 ◽  
Vol 47 (3) ◽  
pp. 555-556
Author(s):  
Lado Ruzicka
Keyword(s):  
Sub Saharan Africa ◽  
Sub Saharan

Adolescent Suicidality as Seen in Rural Northeastern Uganda

Crisis ◽  
2011 ◽  
Vol 32 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Eugene Kinyanda ◽  
Ruth Kizza ◽  
Jonathan Levin ◽  
Sheila Ndyanabangi ◽  
Catherine Abbo
Keyword(s):  
Low Socioeconomic Status ◽  
Sub Saharan Africa ◽  
Psychosocial Risk ◽  
Psychiatric Nurses ◽  
Health Concern ◽  
Cross Sectional ◽  
Childhood Experiences ◽  
Low Socioeconomic ◽  
Dsm Iv ◽  
Sub Saharan

Background: Suicidal behavior in adolescence is a public health concern and has serious consequences for adolescents and their families. There is, however, a paucity of data on this subject from sub-Saharan Africa, hence the need for this study. Aims: A cross-sectional multistage survey to investigate adolescent suicidality among other things was undertaken in rural northeastern Uganda. Methods: A structured protocol administered by trained psychiatric nurses collected information on sociodemographics, mental disorders (DSM-IV criteria), and psychological and psychosocial risk factors for children aged 3–19 years (N = 1492). For the purposes of this paper, an analysis of a subsample of adolescents (aged 10–19 years; n = 897) was undertaken. Results: Lifetime suicidality in this study was 6.1% (95% CI, 4.6%–7.9%). Conclusions: Factors significantly associated with suicidality included mental disorder, the ecological factor district of residence, factors suggestive of low socioeconomic status, and disadvantaged childhood experiences.

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