Analysis of Long-Term Trends of Atmospheric Parameters and Zenith Neutrospheric Delay Including PWV in the Brazilian Region

The neutrosphere, extending from the Earth's surface to about 50 kilometers, includes the dense troposphere and consists mainly of gases and water vapor. Meteorological instruments track these elements, and models like the Global Pressure and Temperature (GPT), based on Numerical Weather Prediction (NWP), represent standard atmospheric conditions. However, these models, heavily reliant on Northern Hemisphere data, and it may often fail to accurately capture Brazil's atmospheric variability due to strong regional and seasonal differences in temperature and humidity. The Amazon rainforest further complicates modeling, making static models inadequate for local conditions. Improving accuracy requires integrating diverse data sources, such as surface weather stations and upper-air observations like radiosondes, to enhance spatial and temporal resolution. This study examines Brazil's neutrospheric variability over ten years, focusing on cities with distinct climates. Northern and Northeastern regions exhibit the highest average temperatures (up to 34.2°C) and air mixing ratios (up to 18.3 g/kg), resulting in significant zenithal delays (ZTD up to 2.5 meters) and high precipitable water vapor (PWV up to 46.8 mm). Southern regions, however, exhibit strong seasonal variability, with summer temperatures averaging 23.3°C and winter temperatures averaging dropping to 13.9°C. PWV varies widely, from 4.2 mm to 106.05 mm. While relative humidity inconsistently reflected seasonal trends, the air mixing ratio reliably captured climatic shifts, averaging 14.6 g/kg in summer and 8.6 g/kg in winter. These variations directly impact signal delay, with ZTD differing by up to 30 centimeters across regions, even within the same period.