Indigenous knowledge in seasonal rainfall prediction in Tanzania : a case of the South-western Highland of Tanzania

Early and significant flowering of Mihemi (Erythrina abyssinica) and Mikwe (Brachystegia speciformis) trees has been identified as a signal of good rainfall in the South-western Highland of Tanzania. Farmers have singled out the behaviour of the Dudumizi bird as another indicator. This study was conducted in Rungwe and Kilolo districts in Mbeya and Iringa regions. Systematic documentation and integration of indigenous knowledge into conventional weather forecasting is a recommended strategy for improving the accuracy and reliability of seasonal rainfall forecasts under increasing climate variability. Since agriculture in Tanzania is mainly rainfed, where, when and what to plant depends on the accuracy of rainfall forecasting

Seasonal forecasts of the rainy season onset over Africa: Preliminary results from the FOCUS-Africa project

Precipitation seasonality is the main factor controlling vegetation phenology in many tropical and subtropical regions. Anticipating the rain onset is of paramount importance for field preparation and seeding. This is of particular importance in various African countries that rely on agriculture as a main source of food, subsistence and income. In such countries, skilful and accurate onset forecasts could also inform early warning and early actions, such as aids logistics planning, for food security. Here, we assess the skill of the seasonal forecast data provided by the Copernicus Climate Change Service in predicting the rain onset over Africa. The skill, i.e. the accuracy of the seasonal forecasts simulation ensemble compared to the climatology, is computed in a probabilistic fashion by accounting for the frequencies of normal, early and late onsets predicted by the forecast system. We compute the skill using the hindcasts (forecast simulations conducted for the past) starting at the beginning of each month in the period 1993–2016. We detect the onset timing of the rainy season using a non-parametric method that accounts for double seasonality and is suitable for the specific time-window of the seasonal forecast simulations. We find positive skills in some key African agricultural regions some months in advance. Overall, the multi-model ensemble outperforms any individual model ensemble. We provide targeted recommendations to develop a useful climate service for the agricultural sector in Africa

Understanding watershed dynamics and impacts of climate change and variability in the Pangani River Basin, Tanzania

Watersheds and rivers are vital ecological features for the provision of hydrological services for the health, welfare and prosperity of human communities. Nevertheless, anthropogenic activities coupled with climate change and climate variability are blamed for degrading watersheds and rivers and decreasing their capacity to irrigate. To address the situation, it is important to understand why and how water shortages are occurring. This paper reports findings of a study carried out to identify and assess drivers of water shortages and adaptation strategies to climate change and variability in Pangani River Basin of Tanzania. To assess the influence of climate change and variability on hydrological flow and water shortages, time series data on rainfall and temperature were compiled from the Tanzania Meteorological Agency. We also used structured questionnaires to collect data on villagers’ perceptions about the drivers of water shortages and adaptation strategies. Results indicated a decreasing trend of water flow (p < 0.05) at Kikuletwa– Karangai gauging station along Pangani River Basin. Trend analysis indicated a slight decrease of rainfall and increase of temperature. Although there is no empirical evidence to associate climate change with the decline of rainfall and water flow, adaptation measures need to be put in place in order to mitigate against increasing climate variability, reduced water flow, and projected climate change. Therefore, watershed conservation strategies should also focus on improving the welfare of local communities. Additionally, involvement of stakeholders in the entire PRB is crucial toward watersheds conservation for steady flow of hydrological services.This article is available at http://www.sciencedirect.com/science/article/pii/S1642359314000834The government of Belgium (scholarship grant number 09TAN/5917) through the Belgium Technical Cooperation (BTC)

Analysis of tropospheric radio refractivity over Julius Nyerere International Airport, Dar es Salaam

meteorological parameters-is of fundamental importance in planning and advancing the understanding of radio wave propagation and wireless communication systems within the troposphere. The vertical profiles of radio refractivity gradient (G) within 1km above the earth’s surface are important for the estimation of anomalous propagation (AP) of microwave radiation. Furthermore the effect of AP in weather radar measurements may be important as spurious echoes from distant ground targets may appear as precipitation leading to incorrect rainfall estimations. AP may also affect dramatically the quality of clear air radar observations. In this paper,we present the vertical and temporal variations of refractive index represented by refractivity (N-units) and refractivity gradient (G) (N-units km-1) in the troposphere to evaluate the occurrence of AP over Julius Nyerere International Airport (JNIA), Dar es Salaam, Tanzania. Meteorological data of air temperature, relative humidity, and atmospheric pressure collected from radiosonde station at JNIA during January, February, August, 2012 and September, October, and November, 2013, were used to compute refractivity, refractive index and refractivity gradient. The percentage of occurrences of super-refraction, sub-refraction, normal-refraction and ducting conditions are presented. Results reveal that, the tropospheric radio wave propagation conditions over JNIA have varying degree of occurrence with normalrefraction conditions prevalent at all the levels except in February, 2012. During this month, super-refraction and normal-refraction conditions have prevailed at the altitude of 1km. The presented results in this paper indicate how the variation in meteorological parameters such as humidity and temperature in the lower troposphere can cause AP. These results can be used by air traffic controllers at: Tanzania Civil Aviation Authority (TCAA) surveillance radar, which is located at JNIA and TMA weather radar, which is located 10km from JNIA, to improve performance of their radars to detect and eliminate false echoes from AP of the radar beam

Strengthening climate services for the food security sector

The Global Framework for Climate Services (GFCS) enables vulnerable sectors and populations to better manage climate variability and adapt to climate change. How? By developing and incorporating science-based climate information into planning, policy and practice. The GFCS places the decision context and information needs of “users” at the centre of the design process. The development of such climate services alters the dynamic between the “user” and the “provider,” valuing each actor's knowledge and engaging them both in a co-production process. This approach challenges the conventional linear supply chain for weather and climate information, in which data are generated, information produced, a product designed, and handed over to the user for consumption, without a real understanding of whether this information is useful for decision-making. In late 2013, with support from the Norwegian Ministry of Foreign Affairs, the GFCS embarked on a multi-agency1 proof of concept. The GFCS Adaptation Programme for Africa aimed to increase the resilience of those most vulnerable to the impacts of weather and climate-related hazards, through the development of more effective climate services in Tanzania and Malawi. It focused in particular on the sectors that address food security, health and disaster risk reduction. This article outlines the learning generated through the food security component of the project. The component was jointly led by the World Food Programme (WFP) and CGIAR Research Programme on Climate Change, Agriculture and Food Security (CCAFS), with activities implemented with the Tanzania Meteorological Agency (TMA), Malawian Department of Climate Change and Meteorological Services (DCCMS), and a range of national and local partners

Spatial and Temporal Analysis of Rainfall and Temperature Extreme Indices in Tanzania

Climate extreme indices in Tanzania for the period 1961-2015 are analyzed using quality controlled daily rainfall, maximum and minimum temperatures data. RClimdex and National Climate Monitoring Products (NCMP) software developed by the commission for Climatology of the World Meteorological Organization (WMO) were used for the computation of the indices at the respective stations at monthly and annual time scales. The trends of the extreme indices averaged over the country were computed and tested for statistical significance. Results showed a widespread statistical significant increase in temperature extremes consistent with global warming patterns. On average, the annual timescale indicate that mean temperature anomaly has increased by 0.69˚C, mean percentage of warm days has increased by 9.37%, and mean percentage of warm nights has increased by 12.05%. Mean percentage of cold days and nights have decreased by 7.64% and 10.00% respectively. A non-statistical significance decreasing trends in rainfall is depicted in large parts of the country. Increasing trend in percentage of warm days and warm nights is mostly depicted over the eastern parts of the country including areas around Kilimanjaro, Dar-es-Salaam, Zanzibar, Mtwara, and Mbeya regions. Some parts of the Lake Victoria Basin are also characterized by increasing trend of warm days and warm nights. However, non-statistical significant decreasing trends in the percentage of warm days and warm nights are depicted in the western parts of the country including Tabora and Kigoma regions and western side of the lake Victoria. These results indicate a clear dipole pattern in temperature dynamics between the eastern side of the country mainly influenced by the Indian Ocean and the western side of the country largely influenced by the moist Congo air mass associated with westerly winds. The results also indicate that days and nights are both getting warmer, though, the warming trend is much faster in the minimum temperature than maximum temperature.The paper is publishedThe authors wish to thank The Tanzania Meteorological Agency for providing data used in this study and WMO for providing guidance in the analysis of climate extreme in climate time series