Fang, X., J.W. Pomeroy, C.R. Ellis, M.K. MacDonald, C.M. DeBeer, and T. Brown, 2013: “Multi-variable evaluation of hydrological model predictions for a headwater basin in the Canadian Rocky Mountains.” Hydrology and Earth System Sciences, v. 17, pp. 1635-1659, doi: 10.5194/hess-17-1635-2013.
One of the purposes of the Cold Regions Hydrological Modelling platform (CRHM) is to diagnose inadequacies in the understanding of the hydrological cycle and its simulation. A physically based hydrological model including a full suite of snow and cold regions hydrology processes as well as warm season, hillslope and groundwater hydrology was developed in CRHM for application in the Marmot Creek Research Basin (~9.4 km2), located in the Front Ranges of the Canadian Rocky Mountains. Parameters were selected from digital elevation model, forest, soil, and geological maps, and from the results of many cold regions hydrology studies in the region and elsewhere. Non-calibrated simulations were conducted for six hydrological years during the period 2005–2011 and were compared with detailed field observations of several hydrological cycle components. The results showed good model performance for snow accumulation and snowmelt compared to the field observations for four seasons during the period 2007–2011, with a small bias and normalised root mean square difference (NRMSD) ranging from 40 to 42% for the subalpine conifer forests and from 31 to 67% for the alpine tundra and treeline larch forest environments. Overestimation or underestimation of the peak SWE ranged from 1.6 to 29%. Simulations matched well with the observed unfrozen moisture fluctuation in the top soil layer at a lodgepole pine site during the period 2006–2011, with a NRMSD ranging from 17 to 39%, but with consistent overestimation of 7 to 34%. Evaluations of seasonal streamflow during the period 2006–2011 revealed that the model generally predicted well compared to observations at the basin scale, with a NRMSD of 60% and small model bias (1%), while at the sub-basin scale NRMSDs were larger, ranging from 72 to 76%, though overestimation or underestimation for the cumulative seasonal discharge was within 29%. Timing of discharge was better predicted at the Marmot Creek basin outlet, having a Nash–Sutcliffe efficiency (NSE) of 0.58 compared to the outlets of the sub-basins where NSE ranged from 0.2 to 0.28. The Pearson product-moment correlation coefficient of 0.15 and 0.17 for comparisons between the simulated groundwater storage and observed groundwater level fluctuation at two wells indicate weak but positive correlations. The model results are encouraging for uncalibrated prediction and indicate research priorities to improve simulations of snow accumulation at treeline, groundwater dynamics, and small-scale runoff generation processes in this environment. The study shows that improved hydrological cycle model prediction can be derived from improved hydrological understanding and therefore is a model that can be applied for prediction in ungauged basins.
Boike, J., B. Kattenstroth, K. Abramova, N. Bornemann, A. Chetverova, T. Fedorova, K. Fröb, M. Grigoriev, M. Grüber, L. Kutzbach, M. Langer, M. Minke, S. Muster, K. Piel, E.-M. Pfeiffer, G. Stoof, S. Westermann, K. Wischnewski, C. Wille, and H.-W. Hubberten, 2013: “Baseline characteristics of climate, permafrost and land cover from a new permafrost observatory in the Lena River Delta, Siberia (1998–2011).” Biogeosciences, v. 10, pp. 2105-2128, doi: 10.5194/bg-10-2105-2013.
Samoylov Island is centrally located within the Lena River Delta at 72° N, 126° E and lies within the Siberian zone of continuous permafrost. The landscape on Samoylov Island consists mainly of late Holocene river terraces with polygonal tundra, ponds and lakes, and an active floodplain. The island has been the focus of numerous multidisciplinary studies since 1993, which have focused on climate, land cover, ecology, hydrology, permafrost and limnology. This paper aims to provide a framework for future studies by describing the characteristics of the island’s meteorological parameters (temperature, radiation and snow cover), soil temperature, and soil moisture. The land surface characteristics have been described using high resolution aerial images in combination with data from ground-based observations. Of note is that deeper permafrost temperatures have increased between 0.3 to 1.3 °C over the last five years. However, no clear warming of air and active layer temperatures is detected since 1998, though winter air temperatures during recent years have not been as cold as in earlier years.
Wang, B., J. Liu, H.-J. Kim, P.J. Webster, S.-Y. Yim, and B. Xiang, 2013: “Northern Hemisphere summer monsoon intensified by mega-El Niño/southern oscillation and Atlantic multidecadal oscillation.” Proceedings of the National Academy of Sciences, v. 110, pp. 5347-5352, 10.1073/pnas.1219405110.
Prediction of monsoon changes in the coming decades is important for infrastructure planning and sustainable economic development. The decadal prediction involves both natural decadal variability and anthropogenic forcing. Hitherto, the causes of the decadal variability of Northern Hemisphere summer monsoon (NHSM) are largely unknown because the monsoons over Asia, West Africa, and North America have been studied primarily on a regional basis, which is unable to identify coherent decadal changes and the overriding controls on planetary scales. Here, we show that, during the recent global warming of about 0.4 °C since the late 1970s, a coherent decadal change of precipitation and circulation emerges in the entirety of the NHSM system. Surprisingly, the NHSM as well as the Hadley and Walker circulations have all shown substantial intensification, with a striking increase of NHSM rainfall by 9.5% per degree of global warming. This is unexpected from recent theoretical prediction and model projections of the 21st century. The intensification is primarily attributed to a mega-El Niño/Southern Oscillation (a leading mode of interannual-to-interdecadal variation of global sea surface temperature) and the Atlantic Multidecadal Oscillation, and further influenced by hemispherical asymmetric global warming. These factors driving the present changes of the NHSM system are instrumental for understanding and predicting future decadal changes and determining the proportions of climate change that are attributable to anthropogenic effects and long-term internal variability in the complex climate system.
Michalak, A.M., E.J. Anderson, D. Beletsky, S. Boland, N.S. Bosch, T.B. Bridgeman, J.D. Chaffin, K. Cho, R. Confesor, I. Daloğlu, J.V. DePinto, M.A. Evans, G.L. Fahnenstiel, L. He, J.C. Ho, L. Jenkins, T.H. Johengen, K.C. Kuo, E. LaPorte, X. Liu, M.R. McWilliams, M.R. Moore, D.J. Posselt, R.P. Richards, D. Scavia, A.L. Steiner, E. Verhamme, D.M. Wright, and M.A. Zagorski, 2013: “Record-setting algal bloom in Lake Erie caused by agricultural and meteorological trends consistent with expected future conditions.” Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.1216006110.
In 2011, Lake Erie experienced the largest harmful algal bloom in its recorded history, with a peak intensity over three times greater than any previously observed bloom. Here we show that long-term trends in agricultural practices are consistent with increasing phosphorus loading to the western basin of the lake, and that these trends, coupled with meteorological conditions in spring 2011, produced record-breaking nutrient loads. An extended period of weak lake circulation then led to abnormally long residence times that incubated the bloom, and warm and quiescent conditions after bloom onset allowed algae to remain near the top of the water column and prevented flushing of nutrients from the system. We further find that all of these factors are consistent with expected future conditions. If a scientifically guided management plan to mitigate these impacts is not implemented, we can therefore expect this bloom to be a harbinger of future blooms in Lake Erie.
Alexander, K., M. Carzolio, D. Goodin, and E. Vance, 2013: “Climate change is likely to worsen the public health threat of diarrheal disease in Botswana.” International Journal of Environmental Research and Public Health v. 10, pp. 1202-1230, doi: 10.3390/ijerph10041202.
Diarrheal disease is an important health challenge, accounting for the majority of childhood deaths globally. Climate change is expected to increase the global burden of diarrheal disease but little is known regarding climate drivers, particularly in Africa. Using health data from Botswana spanning a 30-year period (1974–2003), we evaluated monthly reports of diarrheal disease among patients presenting to Botswana health facilities and compared this to climatic variables. Diarrheal case incidence presents with a bimodal cyclical pattern with peaks in March (ANOVA p < 0.001) and October (ANOVA p < 0.001) in the wet and dry season, respectively. There is a strong positive autocorrelation (p < 0.001) in the number of reported diarrhea cases at the one-month lag level. Climatic variables (rainfall, minimum temperature, and vapor pressure) predicted seasonal diarrheal with a one-month lag in variables (p < 0.001). Diarrheal case incidence was highest in the dry season after accounting for other variables, exhibiting on average a 20% increase over the yearly mean (p < 0.001). Our analysis suggests that forecasted climate change increases in temperature and decreases in precipitation may increase dry season diarrheal disease incidence with hot, dry conditions starting earlier and lasting longer. Diarrheal disease incidence in the wet season is likely to decline. Our results identify significant health-climate interactions, highlighting the need for an escalated public health focus on controlling diarrheal disease in Botswana. Study findings have application to other arid countries in Africa where diarrheal disease is a persistent public health problem.
Sebastianelli, S., F. Russo, F. Napolitano, and L. Baldini, 2013: “On precipitation measurements collected by a weather radar and a rain gauge network.” Natural Hazards and Earth System Science, v. 13, pp. 605-623, doi: 10.5194/nhess-13-605-2013.
Many phenomena (such as attenuation and range degradation) can influence the accuracy of rainfall radar estimates. They introduce errors that increase as the distance from radar increases, thereby decreasing the reliability of radar estimates for applications that require quantitative precipitation estimation. The present paper evaluates radar error as a function of the range, in order to correct the rainfall radar estimates. The radar is calibrated utilizing data from the rain gauges. Then, the G/R ratio between the yearly rainfall amount measured in each rain gauge position during 2008 and the corresponding radar rainfall amount is calculated against the slant range. The trend of the G/R ratio shows two behaviours: a concave part due to the melting layer effect close to the radar location and an almost linear, increasing trend at greater distances. A best fitting line is used to find an adjustment factor, which estimates the radar error at a given range. The effectiveness of the methodology is verified by comparing pairs of rainfall time series that are observed simultaneously by collocated rain gauges and radar. Furthermore, the variability of the adjustment factor is investigated at the scale of event, both for convective and stratiform events. The main result is that there is not a univocal range error pattern, as it also depends on the characteristics of the considered event. On the other hand, the adjustment factor tends to stabilize itself for time aggregations of the order of one year or greater.
Meybeck, M., M. Kummu, and H.H. Dürr, 2013: “Global hydrobelts and hydroregions: improved reporting scale for water-related issues?” Hydrology and Earth System Science, v. 17, pp. 1093-1111, doi: 10.5194/hess-17-1093-2013.
Global-scale water issues such as its availability, water needs or stress, or management, are mapped at various resolutions and reported at many scales, mostly along political or continental boundaries. As such, they ignore the fundamental heterogeneity of hydroclimates and natural boundaries of river basins. Here we describe the continental landmasses at two levels: eight hydrobelts strictly limited by river basins, defined at a 30’ (0.5°) resolution, which are decomposed on continents as 26 hydroregions. The belts were defined and delineated, based primarily on the annual average temperature (T) and run-off (q), to maximise inter-belt differences and minimise intra-belt variability.
This new global puzzle defines homogeneous and near-contiguous entities with similar hydrological and thermal regimes, glacial and postglacial basin histories, endorheism distribution and sensitivity to climate variations. The mid-latitude, dry and subtropical belts have northern and southern analogues and a general symmetry can be observed for T and q between them. The boreal and equatorial belts are unique. Population density between belts and between the continents varies greatly, resulting in pronounced differences between the belts with analogues in both hemispheres.
Hydroregions (median size 4.7 M km2) are highly contrasted, with the average q ranging between 6 and 1393 mm yr−1 and the average T between −9.7 and +26.3 °C, and a population density ranging from 0.7 to 0.8 p km−2 for the North American boreal region and some Australian hydroregions to 280 p km−2 for some Asian hydroregions. The population/run-off ratio, normalised to a reference pristine region, is used to map and quantify the global population at risk of severe water quality degradation. Our initial tests suggest that hydrobelt and hydroregion divisions are often more appropriate than conventional continental or political divisions for the global analysis of river basins within the Earth system and of water resources.
Suweis, S., A. Rinaldo, A. Maritan, and P. D’Odorico, 2013: “Water-controlled wealth of nations.” Proceeding of the National Academy of Sciences, v. 110, pp. 4230-4233, doi: 10.1073/pnas.1222452110.
Population growth is in general constrained by food production, which in turn depends on the access to water resources. At a country level, some populations use more water than they control because of their ability to import food and the virtual water required for its production. Here, we investigate the dependence of demographic growth on available water resources for exporting and importing nations. By quantifying the carrying capacity of nations on the basis of calculations of the virtual water available through the food trade network, we point to the existence of a global water unbalance. We suggest that current export rates will not be maintained and consequently we question the long-term sustainability of the food trade system as a whole. Water-rich regions are likely to soon reduce the amount of virtual water they export, thus leaving import-dependent regions without enough water to sustain their populations. We also investigate the potential impact of possible scenarios that might mitigate these effects through (i) cooperative interactions among nations whereby water-rich countries maintain a tiny fraction of their food production available for export, (ii) changes in consumption patterns, and (iii) a positive feedback between demographic growth and technological innovations. We find that these strategies may indeed reduce the vulnerability of water-controlled societies.
Lo, M.-H., and J.S. Famiglietti, 2013: “Irrigation in California’s Central Valley strengthens the southwestern U.S. water cycle.” Geophysical Research Letters, v. 40, pp. 301–306, doi: 10.1002/grl.50108.
Characterizing climatological and hydrological responses to agricultural irrigation continues to be an important challenge to understanding the full impact of water management on the Earth’s environment and hydrological cycle. In this study, we use a global climate model, combined with realistic estimates of regional agricultural water use, to simulate the local and remote impacts of irrigation in California’s Central Valley. We demonstrate a clear mechanism that the resulting increase in evapotranspiration and water vapor export significantly impacts the atmospheric circulation in the southwestern United States, including strengthening the regional hydrological cycle. We also identify that irrigation in the Central Valley initiates a previously unknown, anthropogenic loop in the regional hydrological cycle, in which summer precipitation is increased by 15%, causing a corresponding increase in Colorado River streamflow of ~30%. Ultimately, some of this additional streamflow is returned to California via managed diversions through the Colorado River aqueduct and the All-American Canal.
Marshall, J.A., A.J. Castillo, and M.B. Cardenas, 2013: “Assessing student understanding of physical hydrology.” Hydrology and Earth System Sciences, v. 17, pp. 829-836, doi: 10.5194/hess-17-829-2013.
Our objective is to devise a mechanism to characterize and assess upper division and graduate student thinking in hydrology. We accomplish this through development and testing of an assessment tool for a physical hydrology class. The instrument was piloted in two sections of a physical hydrology course. Students were asked to respond to two questions that probed understanding and one question that assessed their ability to apply their knowledge, both prior to and after the course. Student and expert responses to the questions were classified into broad categories to develop a rubric to score responses. Using the rubric, three researchers independently blind-coded the full set of pre- and post-artifacts, resulting in 89% inter-rater agreement on the pre-tests and 83% agreement on the post-tests. The majority of responses made by students at the beginning of the class were characterized as showing only recognition of hydrology concepts from a non-physical perspective; post surveys indicated that the majority had moved to a basic understanding of physical processes, with some students achieving expert understanding. Our study has limitations, including the small number of participants who were all from one institution and the fact that the rubric was still under development. Nevertheless, the high inter-rater agreement from a group of experts indicates that the process we undertook is potentially useful for assessment of learning and understanding physical hydrology.