Process-Informed Subsampling Improves Subseasonal Rainfall Forecasts in Central America.

The predictability of rainy season rainfall over northeast Brazil for the relatively long period 1912–98 is analyzed using dynamical and empirical techniques. The dynamical assessments are based on the HadAM2b atmospheric model forced with the Met Office Global Sea Ice and Sea Surface Temperature Dataset (GISST3). Ensembles of simulations and hindcasts starting from real initial conditions for 1982–93 made under the European Community Prediction of Climate Variations on Seasonal to Interannual Timescales (PROVOST) program are analyzed. The results demonstrate a relatively high degree of predictability. Its source lies mostly in tropical Atlantic and Pacific sea surface temperatures. The results confirm the less extensive evidence of other authors that northeast Brazil is a region where two separate ocean basins influence seasonal climate to a comparable extent. Overall, the sea surface temperature gradient between the northern and southern tropical Atlantic appears to be the more important influence, though El Niño can be dominant when it is strong. These assessments of predictability are consistent with the performance of over a decade of real-time long lead and updated forecasts, issued over the period 1987–98. Multiple regression and linear discriminant analysis prediction techniques, together with model forecasts in the last few years, were used to provide best estimate and probability real-time forecasts of rainy season rainfall. These forecasts had a level of skill that was close to the state of the art in seasonal forecasting

The inherent effects of global sea surface temperature (SST) anomalies on hydrological cycle and vegetation cover complicate the structure of tropical climate at the regional scale. Assessing hydrological processes related to climate forcing is important in Central America because it is surrounded by both the Pacific and Atlantic oceans and two continental landmasses. In this study, the use of high‐resolution remote sensing imagery in wavelet analysis helps identify nonstationary characteristics of hydrological and ecological responses. The wavelet‐based empirical orthogonal function (WEOF) further reflects the nonlinear relationship between the Atlantic and Pacific SST and the greenness of a pristine forested site in Panama, La Amistad International Park. Integrated WEOF and descriptive statistics for data analysis reveal a higher temporal variability in terrestrial precipitation relative to in situ land surface temperature and its probable effects on the presence of dry periods. Such teleconnection signals of SST were identified as a driving force of decline in tropical forest greenness during dry periods. The results of our remote sensing‐based wavelet analysis showed intra‐annual high‐frequency and biennial to triennial low‐frequency signals between enhanced vegetation index/precipitation datasets and SST indices in both Atlantic and Pacific oceans. A spatiotemporal priority search further confirmed the importance of the effects of the El Niño–Southern Oscillation (ENSO) over terrestrial responses in the selected study site. Coincidence of the effect of ENSO teleconnection patterns on precipitation and vegetation suggests possible impacts of El Niño‐associated droughts in Central America, accompanied by reduced rainfall, especially during the first months of rainy season (June, July, and August), and decline in vegetation cover during the dry season (March and April). Copyright © 2014 John Wiley & Sons, Ltd.

To understand recent climate change in the North Atlantic region and to produce better climate forecasts with uncertainty estimates it is important to determine the atmospheric ‘response’ to Atlantic sea‐surface temperature (SST) forcing. There have been conflicting results regarding the strength, character and tropical‐versus‐extratropical origin of this response. For model‐based studies, this may indicate differing sensitivities to Atlantic SST, but the comparison is complicated by changes in experimental design. Here, a highly controlled experiment with five atmospheric models is undertaken. The influence of realistic (if reasonably strong) and optimally chosen North Atlantic (equator to 70°N) SST anomalies is isolated. Unexpected global agreement between the models is found (e.g. the North Atlantic Oscillation (NAO), Eurasian temperatures, rainfall over the Americas and Africa, and the Asian monsoon). The extratropical North Atlantic region response appears to be associated with remote Caribbean and tropical Atlantic SST anomalies, and with local forcing. Some features such as the European winter‐temperature response would be stronger than atmospheric ‘noise’ if the prescribed SST anomalies persisted for just two years. More generally, Atlantic air–sea interaction appears to be important for climate variability on the 30‐year timescale and, thus, to be important in the climate‐change context. The multi‐model mean response patterns are in reasonable agreement with observational estimates, although the model response magnitudes may be too weak. The similarity between their responses helps to reconcile models. Inter‐model differences do still exist and these are discussed and quantified. © Crown copyright, 2004.

CKD of Unknown Origin in Central America: The Case for a Mesoamerican Nephropathy

Previous studies show that the dominant mode of variability in the Northeastern subtropical Pacific and Atlantic are analogous. Most attention has been given to the wind-evaporation-sea surface temperature (WES) feedback, but more recent studies suggest that clouds and ocean play a role. Here, it is shown that, while the mode of variability is similar, the quantitative role of clouds and ocean are different. Using Community Earth System Model, version 1.2, cloud feedbacks and interactive ocean dynamics are disabled separately to diagnose the relative contributions of each to sea surface temperature (SST) variability in subtropical northeastern ocean basins. Results from four experiments show that the relative contributions from WES and cloud radiative feedback depend on the role of the ocean. Positive cloud radiative feedback is evident in both basins but has less impact on SST variance in the Atlantic than in the Pacific. The reason for this is that ocean processes strongly damp SST anomalies in the Pacific and weakly enhance SST anomalies in the Atlantic. When cloud feedbacks are disabled, ocean processes become a larger driver of SST variability in the Atlantic. In line with previous studies, the Northeast Pacific SST variability may be understood as a white-noise-forced linear stochastic system with positive feedback from cloud and damping by latent heat flux and ocean processes, while Atlantic SST is driven partially by variations in ocean circulation and requires vertical mixing for rendition. Between these two regions, different ocean dynamics lead to different roles for atmospheric feedbacks but still result in similar patterns of SST variability.

Abstract. A simple two-dimensional rainfall model, based on advection and conservation of mass in a vertical cloud column, is investigated for use in short-term rainfall and flood forecasting at the catchment scale under UK conditions. The model is capable of assimilating weather radar, satellite infra-red and surface weather observations, together with forecasts from a mesoscale numerical weather prediction model, to obtain frequently updated forecasts of rainfall fields. Such data assimilation helps compensate for the simplified model dynamics and, taken together, provides a practical real-time forecasting scheme for catchment scale applications. Various ways are explored for using information from a numerical weather prediction model (16.8 km grid) within the higher resolution model (5 km grid). A number of model variants is considered, ranging from simple persistence and advection methods used as a baseline, to different forms of the dynamic rainfall model. Model performance is assessed using data from the Wardon Hill radar in Dorset for two convective events, on 10 June 1993 and 16 July 1995, when thunderstorms occurred over southern Britain. The results show that (i) a simple advection-type forecast may be improved upon by using multiscan radar data in place of data from the lowest scan, and (ii) advected, steady-state predictions from the dynamic model, using "inferred updraughts", provides the best performance overall. Updraught velocity is inferred at the forecast origin from the last two radar fields, using the mass-balance equation and associated data and is held constant over the forecast period. This inference model proves superior to the buoyancy parameterisation of updraught employed in the original formulation. A selection of the different rainfall forecasts is used as input to a catchment flow forecasting model, the IH PDM (Probability Distributed Moisture) model, to assess their effect on flow forecast accuracy for the 135 km2 Brue catchment in Somerset. Keywords: rainfall forecasting, flood forecasting, weather radar, satellite, storm model

Russian winter snow depth data over a 48-year period (1936–1983) are analysed to reveal variation characteristics and associations to Atlantic sea surface temperature (SST) anomalies using methods of rotated principal component analysis (RPCA), singular spectrum analysis (SSA), and singular value decomposition (SVD) analysis. The study demonstrates that four time scales (4 years interannual, 11.8 years quasidecadal, 20 years bi-decadal and trend) characterize Russian winter snow depth variations. The decadal and longer time scale variations are found to be significantly associated with Atlantic SST anomalies. The trend, which occurred over much of the study region, is associated with SST trends over the northern north and tropical south Atlantic. Bi-decadal snow depth variation over central Siberia is associated with western tropical north Atlantic SSTs. A quasi-decadal variation over western European Russia is connected to a major Atlantic SST variation pattern of opposite signs over alternative latitudinal belts. This study suggests that the connections between the Atlantic Ocean and regional climate may be better reflected at decadal time scales than interannual and seasonal ones, as the dominant variability over the ocean is at slow modes. Copyright © 2000 Royal Meteorological Society

Xylella fastidiosa, a xylem-limited bacterium transmitted by xylem-fluid-feeding Hemiptera insects, causes economic losses of both woody and herbaceous plant species. A Xyl. fastidiosa subsp. pauca strain, namely CoDiRO, was recently found to be associated with the 'olive quick decline syndrome' in southern Italy (i.e. Apulia region). Recently, some Xyl. fastidiosa strains intercepted in France from Coffea spp. plant cuttings imported from Central and South America were characterized. The introduction of infected plant material from Central America in Apulia was also postulated even though an ad hoc study to confirm this hypothesis is lacking. In the present study, we assessed the complete and draft genome of 27 Xyl. fastidiosa strains. Through a genome-wide approach, we confirmed the occurrence of three subspecies within Xyl. fastidiosa, namely fastidiosa, multiplex and pauca, and demonstrated the occurrence of a genetic clonal complex of four Xyl. fastidiosa strains belonging to subspecies pauca which evolved in Central America. The CoDiRO strain displayed 13 SNPs when compared with a strain isolated in Costa Rica from Coffea sp. and 32 SNPs when compared with two strains obtained from Nerium oleander in Costa Rica. These results support the close relationships of the two strains. The four strains in the clonal complex contain prophage-like genes in their genomes. This study strongly supports the possibility of the introduction of Xyl. fastidiosa in southern Italy via coffee plants grown in Central America. The data also stress how the current global circulation of agricultural commodities potentially threatens the agrosystems worldwide.

In this study, the interhemispheric sea surface temperature (SST) signature of the Atlantic Multidecadal Oscillation (AMO) is analyzed and compared between observations and slab ocean model (SOM) simulations. Observational analysis suggests a robust interhemispheric SST dipole across the Atlantic associated with the AMO, manifested by a strong inverse relationship between the AMO and subpolar South Atlantic decadal SST anomalies. None of the SOMs analyzed could reproduce the observed interhemispheric dipole of the AMO; instead, they consistently simulate an interhemispheric coherent SST pattern. In the SOMs, the North Atlantic decadal SST anomalies synchronize the variations of South Atlantic SST through a cross-hemispheric atmosphere teleconnection and thermodynamic processes. This discrepancy between the SOM simulations and the observation is possibly due to deficiencies in representing ocean dynamical processes. Further analyses of the fully coupled versions of the SOMs suggest that the observed interhemispheric dipole of the AMO can be reproduced only by including ocean dynamics related to the Atlantic meridional overturning circulation. Our findings highlight that the ocean dynamics play a non-negligible role and should be taken into consideration in better understanding the observed feature of the AMO.

An approach for improving the capability of a coupled meteorological and hydrological model for rainfall and flood forecasts

The present study investigates the dependence of the northern tropical Atlantic (NTA) sea surface temperature (SST) response to El Nino and La Nina events on the decay time and amplitude of tropical Pacific SST anomalies. It is found that the NTA SST response to La Nina events displays a notable difference between late and early decaying events, similar to that in response to El Nino events, but with a weaker signal. Latent heat flux is a dominant term in the NTA SST change in preceding winter-early spring in both El Nino and La Nina events and in the difference of the NTA SST anomaly between late and early decaying El Nino and La Nina events. The zonal and meridional advections have an opposite effect on the NTA SST warming in late decaying El Nino events. Although the warming in the NTA region is similar in late decaying moderate and strong El Nino events, the distribution of the SST anomalies in the mid-latitude North Atlantic Ocean shows a notable difference between the two types of late decaying El Nino events. The SST anomalies also display difference in the early decaying weak and moderate El Nino events. Surface heat flux differences are largely attributed to wind differences.

Despite the observed high correlation between the Atlantic sea surface temperature (SST) and the Atlantic tropical cyclone (TC) activity, interpretation of this relationship remains uncertain. This study suggests that the tropical Atlantic sea surface warming induces a pair of anomalous low-level cyclones on each side of the equator, providing favorable conditions for enhancing TC formation east of 45°W, while the effect of SST warming in the tropical Indian Ocean and Pacific Ocean tends to suppress the TC formation. Over the past 30 years (1978–2007), the TC activity in the Atlantic basin is characterized with significant enhancement of TC formation east of 45°W, where the total TC number increased significantly compared to the period 1948–77. Despite the possible undercount of TCs, this study shows that the recently enhanced TC formation may not be totally accounted for by the poor TC observing network prior to the satellite era. The Atlantic sea surface warming that occurred in recent decades might have allowed more TCs to form, to form earlier, and to take a longer track, while the effect is partially offset by the SST warming in Indian and Pacific Oceans. This study suggests that the close relationship between the Atlantic SST and TC activity over the past 30 years, including basinwide increases in the average lifetime, annual frequency, proportion of intense hurricanes, and annual accumulated power dissipation index (PDI), as reported in previous studies, is mainly a result of the SST warming in the tropical Atlantic exceeding that in the tropical Indian and Pacific Oceans. The results agree with recent argument that the relative Atlantic SST change or the SST difference between the tropical Atlantic and other oceans play an important role in controlling long-term TC activity in the Atlantic basin.

Cold events occur in North America (NA) frequently, which pose a significant threat to extensive damage to traffic and agriculture. Research on cold events in NA has mainly focused on the individual impacts of the sea surface temperature (SST) variabilities in the North Pacific and the North Atlantic, with less analysis of their synergistic effect. Here we utilize observational data and numerical experiments to show that the positive North Pacific Victoria mode (VM) and the negative North Tropical Atlantic (NTA) SST exert significant synergistic effects on the winter–spring cold events in eastern NA via Rossby waves propagation. Specifically, the VM-related negative western North Pacific (WNP) SST anomalies are linked to upper-tropospheric wind convergence anomalies in situ, which excite a Rossby wave train from the WNP to the North Atlantic and thus strengthen the high-level negative geopotential height anomalies (GHAs) over eastern NA and the positive air-ocean feedback over the North Atlantic. As a result, the negative GHAs strengthened by the positive VM and negative NTA SST cause increased extreme cold events. Further results reveal that the negative GHAs and cold events in eastern NA during the co-occurrence of the positive VM and negative NTA SST events are more than three times stronger than those for the two kinds of single events. This study suggests that the synergistic effect of the positive VM and negative NTA SST anomalies could advance our comprehensive understanding of the combined effect of the inter-basin SST anomalies on the mid-to-high-latitude climate.

Liberalism and Married Women’s Property Rights in Nineteenth-Century Latin America

A prominent precipitation decrease occurred over the equatorial central Pacific in the late 1990s, accompanied by precipitation increase around the Maritime Continent and over the equatorial America. Previous studies attributed the above change to La Nina-like decadal mean sea surface temperature (SST) cooling associated with a positive to negative phase switch of the Pacific Decadal Oscillation (PDO). Results of numerical experiments with an atmospheric general circulation model reveal that both the interdecadal and interannual components of SST variations contribute to the late 1990s’ precipitation reduction over the equatorial central Pacific in all the four seasons and the precipitation increase around the Maritime Continent in winter and summer. The accompanying precipitation increase over the Central America is mainly induced by the interdecadal components of SST variations. The contribution of interannual SST variations to the equatorial central Pacific precipitation decrease mostly stems from a larger rate of precipitation change with SST in positive than negative SST anomaly years, which leads to a residual decadal mean precipitation being larger during the period before than after the late 1990s. The moisture budget decomposition demonstrates that the dynamic effect associated with the vertical motion change dominates the tropical decadal mean precipitation changes in all the four seasons and the thermodynamic effect associated with the moisture change is small. This applies to the equatorial central Pacific, the Maritime Continent, and the Central America in both interdecadal and interannual SST forced simulations.