Temporal resolution refers to the ability of the ultrasound system to distinguish events occurring closely in time. In color flow imaging, temporal resolution is affected by the frame rate, which can be increased by decreasing the width of the color field of view. This is because a narrower color field requires fewer scan lines to be processed, allowing for more frames to be captured per second.
Reference:
ARDMS Sonography Principles and Instrumentation guidelines
Edelman, S. K. (2017). Understanding Ultrasound Physics.