Yes, past about 3000ft, the returned signal is so weak, it has to be integrated out of the noise, over many 1000’s of pulses.
Past 12,000ft the signal is barely detectable, even after integration, unless it its a bigger, far more costly Ceilometer.
Recently, some lower cost systems have come on the market,at much lower cost than the traditional FAA Asos/Awos sytems, ideal for the smaller regional airports.
Just been reading up on this one – Amazing advances over the past few years !!
Another one, that is FAA certified is