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1. Factors Affecting the Weakening Rate of Tropical Cyclones over the Western North Pacific

   https://doi.org/10.1175/MWR-D-19-0356.1  

   Fei, Rong; Xu, Jing; Wang, Yuqing; Yang, Chi (September 2020, Monthly Weather Review)

   null (Ed.)

   Abstract In this study, based on the 6-hourly tropical cyclone (TC) best track data and the ERA-Interim reanalysis data, statistical analyses as well as a machine learning approach, XGBoost, are used to identify and quantify factors that affect the overwater weakening rate (WR) of TCs over the western North Pacific (WNP) during 1980–2017. Statistical analyses show that the TC rapid weakening events usually occur when intense TCs cross regions with a sharp decrease in sea surface temperature (DSST) with relatively faster eastward or northward translational speeds, and move into regions with large environmental vertical wind shear (VWS) and dry conditions in the upshear-left quadrant. Results from XGBoost indicate that the relative intensity of TC (TC intensity normalized by its maximum potential intensity), DSST, and VWS are dominant factors determining TC WR, contributing 26.0%, 18.3%, and 14.9% to TC WR, and 9, 5, and 5 m s−1 day−1 to the variability of TC WR, respectively. Relative humidity in the upshear-left quadrant of VWS, zonal translational speed, divergence at 200 hPa, and meridional translational speed contribute 12.1%, 11.8%, 8.8%, and 8.1% to TC WR, respectively, but only contribute 2–3 m s−1 day−1 to the variability of TC WR individually. These findings suggest that the improved accurate analysis and prediction of the dominant factors may lead to substantial improvements in the prediction of TC WR. 

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2. A comparison of the climate response of longleaf pine (Pinus palustris Mill.) trees among standardized measures of earlywood, latewood, adjusted latewood, and totalwood radial growth

   https://doi.org/https://doi.org/10.1007/s00468-021-02093-z  

   Soule', P.T.; Knapp, P.A.; Maxwell, J.T.; and Mitchell, T.J. (April 2021, Trees)

   null (Ed.)

   Our objective was to examine broadly the climate–growth responses of longleaf pine (Pinus palustris Mill.) on the Coastal Plain province of North and South Carolina to temperature, precipitation, and drought severity. We compared the responses between standardized earlywood, latewood, adjusted latewood, and totalwood radial tree growth. We sampled mature longleaf pine growing in open-canopy savanna environments and developed six tree-ring chronologies using standard dendroecological techniques. We used a combination of Pearson correlation, moving interval correlation, and Fisher r–z tests to determine which monthly and seasonal variables were most closely related to radial growth, the temporal stability of the dominant growth/climate relationship, and whether earlywood and latewood growth provide signifcantly diferent climate responses. Our results show that the strongest relationships with climate are with adjusted latewood growth and that rainfall in the later parts of the growing season (i.e., July–September) is the primary control of radial growth. Spatially, we found that growth/climate responses were similar throughout the Coastal Plain region encompassing the six study sites. Temporally, we found that July–September precipitation produced signifcant (p<0.05) relationships with radial growth for extended annual intervals, but there were shorter periods when this relationship was non-signifcant. In general, growth/ climate relationships were stronger for latewood compared to earlywood, and these responses were signifcantly (p<0.05) diferent at about half of our study sites. Our fndings are congruent with prior research in this region showing that shortduration precipitation events are a critical component for radial growth. Further, these results emphasize the importance of latewood growth—particularly adjusted latewood growth—in capturing interannual climate/growth responses. 

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3. The Longleaf Tree-Ring Network: Reviewing and expanding the utility of Pinus palustris Mill. Dendrochronological data

   https://doi.org/10.1177/03091333221147652  

   Harley, Grant_L; Therrell, Matthew_D; Maxwell, Justin_T; Bhuta, Arvind; Bregy, Joshua_C; Heeter, Karen_J; Patterson, Thomas; Rochner, Maegen; Rother, Monica_T; Stambaugh, Michael; et al (January 2023, Progress in Physical Geography: Earth and Environment)

   The longleaf pine ( Pinus palustris Mill.) and related ecosystem is an icon of the southeastern United States (US). Once covering an estimated 37 million ha from Texas to Florida to Virginia, the near-extirpation of, and subsequent restoration efforts for, the species has been well-documented over the past ca. 100 years. Although longleaf pine is one of the longest-lived tree species in the southeastern US—with documented ages of over 400 years—its use has not been reviewed in the field of dendrochronology. In this paper, we review the utility of longleaf pine tree-ring data within the applications of four primary, topical research areas: climatology and paleoclimate reconstruction, fire history, ecology, and archeology/cultural studies. Further, we highlight knowledge gaps in these topical areas, for which we introduce the Longleaf Tree-Ring Network (LTRN). The overarching purpose of the LTRN is to coalesce partners and data to expand the scientific use of longleaf pine tree-ring data across the southeastern US. As a first example of LTRN analytics, we show that the development of seasonwood chronologies (earlywood width, latewood width, and total width) enhances the utility of longleaf pine tree-ring data, indicating the value of these seasonwood metrics for future studies. We find that at 21 sites distributed across the species’ range, latewood width chronologies outperform both their earlywood and total width counterparts in mean correlation coefficient (RBAR = 0.55, 0.46, 0.52, respectively). Strategic plans for increasing the utility of longleaf pine dendrochronology in the southeastern US include [1] saving remnant material ( e.g., stumps, logs, and building construction timbers) from decay, extraction, and fire consumption to help extend tree-ring records, and [2] developing new chronologies in LTRN spatial gaps to facilitate broad-scale analyses of longleaf pine ecosystems within the context of the topical groups presented. 

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4. A Global Perspective of Tropical Cyclone Precipitation in Reanalyses

   https://doi.org/10.1175/JCLI-D-20-0892.1  

   Jones, Evan; Wing, Allison A.; Parfitt, Rhys (November 2021, Journal of Climate)

   Abstract This study compares the spread in climatological tropical cyclone (TC) precipitation across eight different reanalysis datasets: NCEP-CFSR, ERA-20C, ERA-40, ERA5, ERA-Interim, JRA-55, MERRA-2, and NOAA-20C. TC precipitation is assigned using manual tracking via a fixed 500-km radius from each TC center. The reanalyses capture similar general spatial patterns of TC precipitation and TC precipitation fraction, defined as the fraction of annual precipitation assigned to TCs, and the spread in TC precipitation is larger than the spread in total precipitation across reanalyses. The spread in TC precipitation relative to the inter-reanalysis mean TC precipitation, or relative spread, is larger in the east Pacific than in the west Pacific. Partitioned by reanalysis intensity, the largest relative spread across reanalyses in TC precipitation is from high-intensity TCs. In comparison with satellite observations, reanalyses show lower climatological mean annual TC precipitation over most areas. A comparison of area-averaged precipitation rate in TCs composited over reanalysis intensity shows the spread across reanalyses is larger for higher intensity TCs. Testing the sensitivity of TC precipitation assignment to tracking method shows that climatological mean annual TC precipitation is systematically larger when assigned via manual tracking versus objective tracking. However, this tendency is minimized when TC precipitation is normalized by TC density. Overall, TC precipitation in reanalyses is affected by not only horizontal output resolution or any TC preprocessing, but also data assimilation and parameterization schemes. The results indicate that improvements in the representation of TCs and their precipitation in reanalyses are needed to improve overall precipitation. 

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5. Seasonal Hydroclimate Recorded in High Resolution δ ¹⁸ O Profiles Across Pinus palustris Growth Rings

   https://doi.org/10.1029/2021JG006505  

   Lukens, William E.; Narmour, Robert T.; Schubert, Brian A. (December 2021, Journal of Geophysical Research: Biogeosciences)

   Abstract Rainfall amount and intensity are increasing under anthropogenic climate change, but many instrument records span less than a century. The oxygen isotopic composition of tree‐ring cellulose (δ¹⁸O_cell) reflects local source water, climate, and tree physiology. The patterns of δ¹⁸O_cellwithin tree‐rings has the potential to extend pre‐instrument climate records with subannual resolution, but the influences on intra‐ring δ¹⁸O_cellprofiles are unexplored in many settings. In this study, high‐resolution δ¹⁸O_cellprofiles were analyzed on three longleaf pine trees growing in a native savanna in Louisiana, United States. The time series covers a wide range of rainfall conditions from 2001 to 2008 C.E. with a total of 421 δ¹⁸O_cellanalyses. The δ¹⁸O_cellvalues for individual years are well correlated with each other both within and between trees (r = 0.71–0.78). We used principal components analysis andk‐means clustering to differentiate δ¹⁸O_cellprofiles into two groupings: symmetrical δ¹⁸O_cellprofiles versus asymmetrical profiles that have depressed latewood δ¹⁸O_cellvalues. The slope of latewood δ¹⁸O_cellprofiles and mean δ¹⁸O_cellvalues of latewood tissue correlate with total June‐November precipitation. We hypothesize that poorly drained soils in the study area mediate the influence of any individual storm event: in dry years,¹⁸O‐depleted signals from convective storms are moderated by subsequent evaporative enrichment of standing water, whereas in wet years, increased humidity and frequent re‐supply of¹⁸O‐depleted water overrides evaporative enrichment effects, resulting in low δ¹⁸O_cellof latewood. These results suggest that δ¹⁸O_cellproxies for tropical storm occurrence need to account for soil conditions at the site of tree growth. 

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