TITLE:
An Interannual Dipole Pattern of September-November Surface Maximum Air Temperature Anomalies across Tanzania and the Associated Atmospheric Conditions
AUTHORS:
Haji Suleiman Jecha, Mtupili Msafiri
KEYWORDS:
Maximum Temperature, Climate Variability, September-November (SON), Atmospheric Circulation, Surface Energy Fluxes, Cloud-Radiation Feedback
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.14 No.1,
January
22,
2026
ABSTRACT: This study presents a comprehensive analysis of the spatio-temporal patterns and governing mechanisms of September-November (SON) maximum temperature (Tmax) variability across Tanzania from 1979 to 2024. Climatologically, SON is the hottest season for Tanzania’s interior, characterized by a strong thermal gradient from the persistently hot central plateau (mean Tmax > 32˚C) to the moderated coastal zones and cool highlands. Empirical Orthogonal Function analysis of SON Tmax anomalies reveals a dominant, spatially uniform pattern and a robust dipole pattern critical for interannual extremes. This dipole features out-of-phase Tmax anomalies between the central/southern interior and the northeastern/coastal regions. Correlation analysis shows the interannual component of this dipole mode (PC2) exhibits distinct extreme events but weak collective linear forcing from standard tropical climate indices (explained variance ~7.8%), with its strongest but highly non-stationary contemporaneous link to the NINO12 index. Lagged correlations suggest indices like the Dipole Mode Index may act as precursor forcings. Physically, the positive dipole phase is initiated by increased surface net longwave radiation, driven by anomalous cloudiness from modulated atmospheric dynamics. Anomalous low-level easterly/northeasterly winds transport warm, moist air from the Indian Ocean, leading to lower-tropospheric moistening, ascent above 700 hPa, and enhanced cloud cover that alters surface radiation. The increased net radiative energy is partitioned preferentially into sensible heat flux, directly warming the near-surface air. These findings underscore that regional heat extremes are shaped by a complex interplay of remote teleconnections and local circulation-cloud-radiation interactions, with implications for forecasting and projecting extreme heat over Tanzania’s vulnerable interior.