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Stephen W Nesbitt

Publications and source records attributed to Stephen W Nesbitt.

2 recordsLinked to original sources

Navigating Through Turbulence: Charting Early Careers in Weather and Climate Science

The field of weather and climate science is at a pivotal moment, defined by simultaneous forces of institutional disruption and unprecedented technological advancements. While a shifting research and employment landscape has created career uncertainty, prompting many scientists to consider or pursue opportunities in the private sector, it has simultaneously spurred an expansion of the ecosystem through the emergence of new computational tools and the growing role of industry innovators and stakeholders. This perspective paper argues that this new, expanded ecosystem presents extraordinary opportunities for students and early-career professionals. We outline the emerging scientific frontiers powered by high-resolution simulations and artificial intelligence, suggest a practical path for navigating a more fluid career landscape, and propose how education and training must evolve. We argue that these changes expand rather than diminish the reader's capacity to do what drew most of us to this field: helping people prepare for what the atmosphere is about to do.

physics.ao-ph

Dry-to-Wet Soil Gradients Enhance Convection and Rainfall over Subtropical South America

Soil moisture-precipitation (SM-PPT) feedbacks at the mesoscale represent a major challenge for numerical weather prediction, especially for subtropical regions that exhibit large variability in surface SM. How does surface heterogeneity, specifically mesoscale gradients in SM and land surface temperature (LST), affect convective initiation (CI) over South America? Using satellite data, we track nascent, daytime convective clouds and quantify the underlying antecedent (morning) surface heterogeneity. We find that convection initiates preferentially on the dry side of strong SM/LST boundaries with spatial scales of tens of kilometers. The strongest alongwind gradients in LST anomalies at 30 km length scale underlying the CI location occur during weak background low-level wind (<2.5m/s), high convective available potential energy (>1500J/kg) and low convective inhibition (<250J/kg) over sparse vegetation. At 100 km scale, strong gradients occur at the CI location during convectively unfavorable conditions and strong background flow. The location of PPT is strongly sensitive to the strength of the background flow. The wind profile during weak background flow inhibits propagation of convection away from the dry regions leading to negative SM-PPT feedback whereas strong background flow is related to longer lifecycle and rainfall hundreds of kilometers away from the CI location. Thus, the sign of the SM-PPT feedback is dependent on the background flow. This work presents the first observational evidence that CI over subtropical South America is associated with dry soil patches on the order of tens of kilometers. Convection-permitting numerical weather prediction models need to be examined for accurately capturing the effect of SM heterogeneity in initiating convection over such semi-arid regions.

physics.ao-ph