Haiqin Li

The Global/Regional Integrated Model system (GRIMs)

A multiscale atmospheric/oceanic model system with unified physics, the Global/Regional Integrated Model system (GRIMs) has been created for use in numerical weather prediction, seasonal simulations, and climate research projects, from global to regional scales. It includes not only the model code, but also the test cases and scripts. The model system is developed and practiced by taking advantage of both operational and research applications. This article outlines the history of GRIMs, its current applications, and plans for future development, providing a summary useful to present and future users.

Seasonal Hydrological Forecasts for Watersheds over the Southeastern United States for the Boreal Summer and Fall Seasons

AbstractThe authors evaluate the skill of a suite of seasonal hydrological prediction experiments over 28 watersheds throughout the southeastern United States (SEUS), including Florida, Georgia, Alabama, South Carolina, and North Carolina. The seasonal climate retrospective forecasts [the Florida Climate Institute–Florida State University Seasonal Hindcasts at 50-km resolution (FISH50)] is initialized in June and integrated through November of each year from 1982 through 2001. Each seasonal climate forecast has six ensemble members. An earlier study showed that FISH50 represents state-of-the-art seasonal climate prediction skill for the summer and fall seasons, especially in the subtropical and higher latitudes. The retrospective prediction of streamflow is based on multiple calibrated rainfall–runoff models. The hydrological models are forced with rainfall from FISH50, (quantile based) bias-corrected FISH50 rainfall (FISH50_BC), and resampled historical rainfall observations based on matching observed an...

The seasonal climate predictability of the Atlantic Warm Pool and its teleconnections

Our study reveals that there is promising seasonal predictability of the Atlantic Warm Pool (AWP; defined as the area enclosed by the 28.5°C isotherm in tropical western Atlantic) and its associated teleconnections of late summer-early fall seasonal rainfall anomalies over the continental US displayed by a subset of the North American Multi-Model Ensemble (NMME). We find that of the four NMME models at least two models (CFSv2 and GFDL) exhibit consistently useful deterministic and probabilistic skill in predicting the July-October (JASO) seasonal anomalies of the area of the AWP at lead times of up to four months. These two models shown are shown to beat the observed persistence skill by a significant margin at all lead times with the exception of lead time zero. The two NMME models also skillfully predict the teleconnections of the JASO AWP anomalies with the corresponding seasonal JASO rainfall anomalies in the eastern Mississippi valley. These prediction skills are significant improvement in warm season rainfall predictability over the continental US.

Santa Ana Winds of Southern California: Their climatology, extremes, and behavior spanning six and a half decades

Santa Ana Winds (SAWs) are an integral feature of the regional climate of Southern California/Northern Baja California region, but their climate-scale behavior is poorly understood. In the present work, we identify SAWs in mesoscale dynamical downscaling of a global reanalysis from 1948 to 2012. Model winds are validated with anemometer observations. SAWs exhibit an organized pattern with strongest easterly winds on westward facing downwind slopes and muted magnitudes at sea and over desert lowlands. We construct hourly local and regional SAW indices and analyze elements of their behavior on daily, annual, and multidecadal timescales. SAWs occurrences peak in winter, but some of the strongest winds have occurred in fall. Finally, we observe that SAW intensity is influenced by prominent large-scale low-frequency modes of climate variability rooted in the tropical and north Pacific ocean-atmosphere system.

The precursors in the Intra‐Americas Seas to seasonal climate variations over North America

In this paper, we show from observations that the Intra-American Seas precursor as characterized by the onset of the Atlantic Warm Pool (AWP; defined by the area enclosed by 28.5°C isotherm in the tropical Atlantic Ocean) has discernible impact on the boreal summer and fall seasonal climate variations over North America, a season and a region well known for relatively poor seasonal predictability. The onset of the AWP season is objectively defined as the day when the daily anomaly of the AWP area, west of 50°W, and north of the equator exceeds its climatological annual mean value. We show that early (late) onset of AWP is associated with following August-September-October (ASO) deficit (excess) seasonal rainfall anomalies over southern Mississippi valley extending to the Midwest US east of Iowa. On the other hand, Central America and the Caribbean region exhibit enhanced (decreased) ASO seasonal mean rainfall during an early (late) onset of AWP. We also find that early (late) onset of the AWP is associated with early (late) onset and early (late) demise of the rainy season over Mesoamerica. This relationship also leads to association of early (late) onset of AWP with increased (shortened) length of the rainy season over Mesoamerica. These teleconnections are dictated by the modulation of the low-level flow and moisture flux convergence associated with the varying development of the AWP. Similarly, we find that early (late) onset years of the AWP are associated with a more active (inactive) seasonal Atlantic tropical cyclone activity. These teleconnections are sustained from the fact that the AWP onset date variations are found to be a precursor to the seasonal AWP size variations.

The seasonal predictability of the Asian summer monsoon in a two-tiered forecast system

An extensive set of boreal summer seasonal hindcasts from a two tier system is compared with corresponding seasonal hindcasts from two other coupled ocean–atmosphere models for their seasonal prediction skill (for precipitation and surface temperature) of the Asian summer monsoon. The unique aspect of the two-tier system is that it is at relatively high resolution and the SST forcing is uniquely bias corrected from the multi-model averaged forecasted SST from the two coupled ocean–atmosphere models. Our analysis reveals: (a) The two-tier forecast system has seasonal prediction skill for precipitation that is comparable (over the Southeast Asian monsoon) or even higher (over the South Asian monsoon) than the coupled ocean–atmosphere. For seasonal anomalies of the surface temperature the results are more comparable across models, with all of them showing higher skill than that for precipitation. (b) Despite the improvement from the uncoupled AGCM all models in this study display a deterministic skill for seasonal precipitation anomalies over the Asian summer monsoon region to be weak. But there is useful probabilistic skill for tercile anomalies of precipitation and surface temperature that could be harvested from both the coupled and the uncoupled climate models. (c) Seasonal predictability of the South Asian summer monsoon (rainfall and temperature) does seem to stem from the remote ENSO forcing especially over the Indian monsoon region and the relatively weaker seasonal predictability in the Southeast Asian summer monsoon could be related to the comparatively weaker teleconnection with ENSO. The uncoupled AGCM with the bias corrected SST is able to leverage this teleconnection for improved seasonal prediction skill of the South Asian monsoon relative to the coupled models which display large systematic errors of the tropical SST’s.

Catalina Eddy as revealed by the historical downscaling of reanalysis

Climatological properties, dynamical and thermodynamical characteristics of the Catalina Eddy are examined from the 61 years NCEP/NCAR Reanalysis downscaled to hourly 10 km resolution. The eddy is identified as a mesoscale cyclonic circulation confined to the Southern California Bight. Pattern correlation of wind direction against the canonical Catalina Eddy is used to extract cases from the downscaled analysis. Validation against published cases and various observations confirmed that the downscaled analysis accurately reproduces Catalina Eddy events. A composite analysis of the initiation phase of the eddy indicates that no apparent large-scale cyclonic/anti-cyclonic large-scale forcing is associated with the eddy formation or decay. The source of the vorticity is located at the coast of the Santa Barbara Channel. It is generated by the convergence of the wind system crossing over the San Rafael Mountains and the large-scale northwesterly flow associated with the subtropical high. This vorticity is advected towards the southeast by the northwesterly flow, which contributes to the formation of the streak of positive vorticity. At 6 hours prior to the mature stage, there is an explosive generation of positive vorticity along the coast, coincident with the phase change of the sea breeze circulation (wind turning from onshore to offshore), resulting in the convergence all along the California coast. The generation of vorticity due to convergence along the coast together with the advection of vorticity from the north resulted in the formation of southerly flow along the coast, forming the Catalina Eddy. The importance of diurnal variation and the lack of large-scale forcing are new findings, which are in sharp contrast to prior studies. These differences are due to the inclusion of many short-lived eddy events detected in our study which have not been included in other studies.