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Climate, Volume 2, Issue 3 (September 2014) – 6 articles , Pages 129-222

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867 KiB  
Article
Spatial-Temporal Variation and Prediction of Rainfall in Northeastern Nigeria
by Umar M. Bibi, Jörg Kaduk and Heiko Balzter
Climate 2014, 2(3), 206-222; https://doi.org/10.3390/cli2030206 - 17 Sep 2014
Cited by 18 | Viewed by 8624
Abstract
In Northeastern Nigeria seasonal rainfall is critical for the availability of water for domestic use through surface and sub-surface recharge and agricultural production, which is mostly rain fed. Variability in rainfall over the last 60 years is the main cause for crop failure [...] Read more.
In Northeastern Nigeria seasonal rainfall is critical for the availability of water for domestic use through surface and sub-surface recharge and agricultural production, which is mostly rain fed. Variability in rainfall over the last 60 years is the main cause for crop failure and water scarcity in the region, particularly, due to late onset of rainfall, short dry spells and multi-annual droughts. In this study, we analyze 27 years (1980–2006) of gridded daily rainfall data obtained from a merged dataset by the National Centre for Environmental Prediction and Climate Research Unit reanalysis data (NCEP-CRU) for spatial-temporal variability of monthly amounts and frequency in rainfall and rainfall trends. Temporal variability was assessed using the percentage coefficient of variation and temporal trends in rainfall were assessed using maps of linear regression slopes for the months of May through October. These six months cover the period of the onset and cessation of the wet season throughout the region. Monthly rainfall amount and frequency were then predicted over a 24-month period using the Auto Regressive Integrated Moving Average (ARIMA) Model. The predictions were evaluated using NCEP-CRU data for the same period. Kolmogorov Smirnov test results suggest that despite there are some months during the wet season (May–October) when there is no significant agreement (p < 0.05) between the monthly distribution of the values of the model and the corresponding 24-month NCEP-CRU data, the model did better than simply replicating the long term mean of the data used for the prediction. Overall, the model does well in areas and months with lower temporal rainfall variability. Maps of the coefficient of variation and regression slopes are presented to indicate areas of high rainfall variability and water deficit over the period under study. The implications of these results for future policies on Agriculture and Water Management in the region are highlighted. Full article
(This article belongs to the Special Issue Changes in Precipitation and Impacts on Regional Water Resources)
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1995 KiB  
Article
On the Equality Assumption of Latent and Sensible Heat Energy Transfer Coefficients of the Bowen Ratio Theory for Evapotranspiration Estimations: Another Look at the Potential Causes of Inequalities
by Suat Irmak, Ayse Kilic and Sumantra Chatterjee
Climate 2014, 2(3), 181-205; https://doi.org/10.3390/cli2030181 - 29 Aug 2014
Cited by 24 | Viewed by 6530
Abstract
Evapotranspiration (ET) and sensible heat (H) flux play a critical role in climate change; micrometeorology; atmospheric investigations; and related studies. They are two of the driving variables in climate impact(s) and hydrologic balance dynamics. Therefore, their accurate estimate is [...] Read more.
Evapotranspiration (ET) and sensible heat (H) flux play a critical role in climate change; micrometeorology; atmospheric investigations; and related studies. They are two of the driving variables in climate impact(s) and hydrologic balance dynamics. Therefore, their accurate estimate is important for more robust modeling of the aforementioned relationships. The Bowen ratio energy balance method of estimating ET and H diffusions depends on the assumption that the diffusivities of latent heat (KV) and sensible heat (KH) are always equal. This assumption is re-visited and analyzed for a subsurface drip-irrigated field in south central Nebraska. The inequality dynamics for subsurface drip-irrigated conditions have not been studied. Potential causes that lead KV to differ from KH and a rectification procedure for the errors introduced by the inequalities were investigated. Actual ET; H; and other surface energy flux parameters using an eddy covariance system and a Bowen Ratio Energy Balance System (located side by side) on an hourly basis were measured continuously for two consecutive years for a non-stressed and subsurface drip-irrigated maize canopy. Most of the differences between KV and KH appeared towards the higher values of KV and KH. Although it was observed that KV was predominantly higher than KH; there were considerable data points showing the opposite. In general; daily KV ranges from about 0.1 m2∙s−1 to 1.6 m2∙s−1; and KH ranges from about 0.05 m2∙s−1 to 1.1 m2∙s−1. The higher values for KV and KH appear around March and April; and around September and October. The lower values appear around mid to late December and around late June to early July. Hourly estimates of KV range between approximately 0 m2∙s−1 to 1.8 m2∙s−1 and that of KH ranges approximately between 0 m2∙s−1 to 1.7 m2∙s−1. The inequalities between KV and KH varied diurnally as well as seasonally. The inequalities were greater during the non-growing (dormant) seasons than those during the growing seasons. During the study period, KV was, in general, lesser than KH during morning hours and was greater during afternoon hours. The differences between KV and KH mainly occurred in the afternoon due to the greater values of sensible heat acting as a secondary source of energy to vaporize water. As a result; during the afternoon; the latent heat diffusion rate (KV) becomes greater than the sensible heat diffusion rate (KH). The adjustments (rectification) for the inequalities between eddy diffusivities is quite essential at least for sensible heat estimation, and can have important implications for application of the Bowen ratio method for estimation of diffusion fluxes of other gasses. Full article
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1067 KiB  
Article
California Getting Wetter to the North, Drier to the South: Natural Variability or Climate Change?
by Dan Killam, Ann Bui, Steve LaDochy, Pedro Ramirez, Joshua Willis and William Patzert
Climate 2014, 2(3), 168-180; https://doi.org/10.3390/cli2030168 - 27 Aug 2014
Cited by 37 | Viewed by 11516
Abstract
Current climate change projections anticipate that global warming trends will lead to changes in the distribution and intensity of precipitation at a global level. However, few studies have corroborated these model-based results using historical precipitation records at a regional level, especially in our [...] Read more.
Current climate change projections anticipate that global warming trends will lead to changes in the distribution and intensity of precipitation at a global level. However, few studies have corroborated these model-based results using historical precipitation records at a regional level, especially in our study region, California. In our analyses of 14 long-term precipitation records representing multiple climates throughout the state, we find northern and central regions increasing in precipitation while southern regions are drying. Winter precipitation is increasing in all regions, while other seasons show mixed results. Rain intensity has not changed since the 1920s. While Sacramento shows over 3 more days of rain per year, Los Angeles has almost 4 less days per year in the last century. Both the El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) greatly influence the California precipitation record. The climate change signal in the precipitation records remains unclear as annual variability overwhelms the precipitation trends. Full article
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926 KiB  
Article
The Effect of Land Cover/Land Use Changes on the Regional Climate of the USA High Plains
by Denis Mutiibwa, Ayse Kilic and Suat Irmak
Climate 2014, 2(3), 153-167; https://doi.org/10.3390/cli2030153 - 11 Aug 2014
Cited by 8 | Viewed by 6453
Abstract
We present the detection of the signatures of land use/land cover (LULC) changes on the regional climate of the US High Plains. We used the normalized difference vegetation index (NDVI) as a proxy of LULC changes and atmospheric CO2 concentrations as a [...] Read more.
We present the detection of the signatures of land use/land cover (LULC) changes on the regional climate of the US High Plains. We used the normalized difference vegetation index (NDVI) as a proxy of LULC changes and atmospheric CO2 concentrations as a proxy of greenhouse gases. An enhanced signal processing procedure was developed to detect the signatures of LULC changes by integrating autoregression and moving average (ARMA) modeling and optimal fingerprinting technique. The results, which are representative of the average spatial signatures of climate response to LULC change forcing on the regional climate of the High Plains during the 26 years of the study period (1981–2006), show a significant cooling effect on the regional temperatures during the summer season. The cooling effect was attributed to probable evaporative cooling originating from the increasing extensive irrigation in the region. The external forcing of atmospheric CO2 was included in the study to suppress the radiative warming effect of greenhouse gases, thus, enhancing the LULC change signal. The results show that the greenhouse gas radiative warming effect in the region is significant, but weak, compared to the LULC change signal. The study demonstrates the regional climatic impact of anthropogenic induced atmospheric-biosphere interaction attributed to LULC change, which is an additional and important climate forcing in addition to greenhouse gas radiative forcing in High Plains region. Full article
(This article belongs to the Special Issue Land-Use/Cover Change Impacts on Climate)
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621 KiB  
Article
Influence of Heat Waves on Ischemic Heart Diseases in Germany
by Stefan Zacharias, Christina Koppe and Hans-Guido Mücke
Climate 2014, 2(3), 133-152; https://doi.org/10.3390/cli2030133 - 26 Jun 2014
Cited by 29 | Viewed by 15431
Abstract
The impact of heat waves on ischemic heart disease (IHD) mortality and morbidity in Germany during 2001–2010 is analyzed. Heat waves are defined as periods of at least three consecutive days with daily mean temperature above the 97.5th percentile of the temperature distribution. [...] Read more.
The impact of heat waves on ischemic heart disease (IHD) mortality and morbidity in Germany during 2001–2010 is analyzed. Heat waves are defined as periods of at least three consecutive days with daily mean temperature above the 97.5th percentile of the temperature distribution. Daily excess mortality and morbidity rates are used. All calculations were performed separately for 19 regions to allow for the investigation of regional differences. The results show that IHD mortality during heat waves is significantly increased (+15.2% more deaths on heat wave days). In stark contrast, no heat wave influence on hospital admissions due to IHD could be observed. Regional differences in heat wave IHD mortality are present, with the strongest impact in Western Germany and weaker than average effects in the Southeastern and Northwestern regions. The increase in mortality during heat waves is generally stronger for females (+18.7%) than for males (+11.4%), and for chronic ischemic diseases (+18.4%) than for myocardial infarctions (+12.2%). Longer and more intense heat waves feature stronger effects on IHD mortality, while timing in season seems to be less important. Since climate change will most likely enhance the number and intensity of heat waves, the obtained results point to public adaptation strategies to reduce the future heat wave impact on mortality. Full article
(This article belongs to the Special Issue Climate Impacts on Health)
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161 KiB  
Communication
A Note on the Baseline in Considering the Ice Age
by Syun-Ichi Akasofu
Climate 2014, 2(3), 129-132; https://doi.org/10.3390/cli2030129 - 25 Jun 2014
Cited by 10 | Viewed by 4321
Abstract
Shifting the presently used baselines of temperature changes during the last 440,000 years to about the lowest recorded temperature (+5 °C) as the baseline, a somewhat different view of climate change during the four Ice Ages emerges. Unlike the presently used baselines, the [...] Read more.
Shifting the presently used baselines of temperature changes during the last 440,000 years to about the lowest recorded temperature (+5 °C) as the baseline, a somewhat different view of climate change during the four Ice Ages emerges. Unlike the presently used baselines, the lowest temperature baseline is sort of the “absolute” one, in the sense that it does not depend on any chosen period during the last 440,000 years. Taking such a temperature as the baseline, the general trend of changes represents approximately the heat input function. Thus, in this view, the warming pulses with a sharp onset are the main feature, rather than a sequence of slow cooling and the subsequent sudden warming, although the basic physics involved in the feedback process may be the same. The interglacial periods are the peaks of the impulsive warming, rather than “returning to the normal condition” or “recovery from the Ice Ages”. In fact, the commonly used baselines represent simply the present conditions, rather than the baseline in climatology. Full article
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