Tropical cyclones in the North American Regional Reanalysis: An assessment of spatial biases in location, intensity, and structure

Abstract

Long-term reanalysis data sets, such as the North American Regional Reanalysis (NARR) and Climate Forecast System Reanalysis (CFSR), are data-rich resources for weather and climate research. However, investigations into tropical cyclone (TC) structures are lacking. This study examines position, intensity, and structure of U.S. landfalling TCs in these data sets during 1998-2012. TC positions are determined using three dynamic and thermodynamic parameters. In NARR, positions are problematic near the domain boundary but show statistically significant improvements compared with CFSR in regions over the U.S. and near its coastlines. TC intensity is universally underestimated in both data sets, yet the pressure-wind relationship is reasonably maintained. NARR and CFSR intensities are highly correlated (r = 0.93), suggesting that these data sets are limited in a similar fashion in their generation of intensity and that advanced data assimilation techniques are unable to overcome the shortcomings of low resolutions. To investigate TC structure, a 10-storm composite is constructed using the most intense model TCs at peak intensity. Both models develop robust warm cores (T′~6-7 K), but the radius of maximum winds (>100 km) is too broad compared with storms in nature. Secondary circulation features in NARR are more realistic, particularly the shallow inflow layer, vertical motion in the inner core, and confined outflow in the upper troposphere. Results indicate that, over the U.S. and near its coastline, NARR positions and structure are competitive with or slightly improved upon CFSR. Away from the domain boundary, NARR is a suitable resource for evaluating TC positions and certain aspects of the secondary circulation.

Tropical cyclones in the North American Regional Reanalysis: The impact of satellite‐derived precipitation over ocean

“…Zick and Matyas [] detected spatial biases in the accuracy of TC location (versus BT) in NARR during 1998–2012 due to the limited area model setup and sparse observations/data quality over oceans. When using the same TC tracking methodology and subdividing the analysis period, there are only slight improvements in the mean and median TC position errors during N0412 (Table ).…”

“…Only two storms in each time period (Hurricanes Floyd (1999) and Isabel (2003) in N9803 and Tropical Storm Bonnie (2004) and Hurricane Irene (2011) in N0412) show statistically significant negative correlations. The negative correlations in these four storms may be due to the influence of distance to land, as reanalysis intensities tend to improve as TCs move into more dense observation regions [ Schenkel and Hart , ; Zick and Matyas , ]. Overall, the NARR is able to successfully model TC intensity change in about half of the storms in each period.…”

“…[] and offer compelling evidence that precipitation assimilation could play a supplemental role toward improving the initial temperature, wind, and moisture fields in the vicinity of a TC. Furthermore, we note that Zick and Matyas [] uncovered deficiencies in the Climate Forecast System Reanalysis representation of the TC secondary circulation, even though that reanalysis employs a TC relocation and bogussing scheme. In consideration of this finding and with the results presented herein, future research should continue investigating the utility of precipitation assimilation but in conjunction with TC bogussing.…”

A Nowcasting Model for Tropical Cyclone Precipitation Regions Based on the TREC Motion Vector Retrieval with a Semi-Lagrangian Scheme for Doppler Weather Radar

“…However, recently, the work in [60] pointed out that using composite isothermal reflectivity below 0°C instead of composite reflectivity in QPE improves the correlation in the Z-R relationship due to avoiding the overly high reflectivity values generated by melting hydrometeors around the freezing level [61]. Verification using the North American Regional Reanalysis (NARR) dataset, which has a reasonable representation of TC position and size over the U.S. [62], shows that the 0°C isotherm appears between the altitudes of 4.0 and 4.5 km over the entire analytical domain during the study period. Thus, a composite reflectivity is calculated using data below 4 km.…”

Comparing the Spatial Patterns of Rainfall and Atmospheric Moisture among Tropical Cyclones Having a Track Similar to Hurricane Irene (2011)

“…Reanalysis data with higher spatial resolution, such as the North American Regional Reanalysis and Japanese 25 Year Reanalysis are available for a shorter period of record but would allow a more in-depth study of the spatial dimensions of moisture advection into TC circulations. Research has shown that TCs are well-represented in these datasets, particularly near and over land [76][77][78]. Additionally, radar-derived rain rates, which have a higher spatial and temporal resolution, should be utilized to better identify rainfall events associated with flooding as TCs move over the U.S.…”