What is the format used to express a dew point of -4 degrees Celsius in METAR reporting?

The chosen answer expresses the dew point using a format that clearly identifies both the temperature (T) and the dew point (Td). In this case, "T=2°C, Td=-4°C" conveys that the atmospheric temperature is 2 degrees Celsius, while the dew point is -4 degrees Celsius.

In METAR reports, when providing meteorological conditions, the dew point is often identified as Td, which helps meteorologists and aviators assess moisture in the air. Showing temperatures and dew points together is common practice, and this format is consistent with international reporting standards, making it easy to understand the current conditions and how they might affect weather patterns or aviation safety.

Furthermore, the other options do not accurately convey the dew point of -4 degrees Celsius as required by the question. Some formats either misrepresent the temperatures or do not clearly specify the dew point, which is essential for proper interpretation of weather data.